6Speed's Lectures: How your EVAP system works

[@pctuterman1]

The simplest and best EVAP tutorial I've seen so far. After watching and listening to this video I thought it worthwhile to subscribe to your channel. Keep instructing the way you instructed this video. 👍

[@sasquatchrosefarts]

Quality

[@hitsy_]

Omg this is so helpful and I’m only 1 minute into the video. Love the power point structured presentation! Thank you for this !

[@kid3764]

As a technician, I salute you on a clear and precise presentation. Job well done !

[@SaintBrook]

Thank you so much for this video. I have two cars with codes indicating EVAP system problems and you've helped me understand how the system works before I begin fixing it.

[@tombanes]

I have been searching all day and finally found this content that explained the NVLD . I was mislead by other videos showing more common EVAP systems.

[@YusufFitness]

Thank you for this mate, very well put together.Watched this before going into work to solve an EVAP PROBLEM!

[@beachwave2]

Thank you for the excellent video. The area around my gas cap gets more dirty than usual. A lot of soot or carbon builds up around it and sometimes can even be seen outside the gas cap door. I have changed the gas cap. Any ideas why this keeps happening ? Thank you.

[@tboneproductions2453]

Good video. Good explanation. Just replaced the purge valve on my 2010 Ford Fusion. It was stuck open mechanically. Apparently this is rather common on the Ford purge valves. Ford had a good valve for years ,then did a redesign...... then not so good.Curious if they did another redesign to fix their initial redesign.

[@readchp]

Very clear presentation. No higher compliment to be given on U-tube.

[@stevoidyt]

Excellent video to provide a basic understanding of a car's evap system. Thanks very much.

[@joshdennis9163]

I know this video is a couple years old but awesome job. Something new I've recently seen on a Chevy Cruze with the 1.4 turbo was a bad one way check valve in the purge valve assembly. It was letting unmetered air into the engine and causing a lean condition. Again, great job with the video, just wanted to share a little more insight into some possible failures.

[@laurijorgenson6683]

Thanks for the great tutorial. I have a P0442 code on a 1999 Saab. There are pinholes in the gas tank around the fuel pump area. I presume the tests would show up with a code due to those pinholes. Is that correct?

[@rogjackson]

Excellent video. Extremely helpful information and diagrams are excellent tools for understanding.

[@davidcrane6593]

This is a good video. Thank you. I have a question though... is it normal procedure for a car to run a Constant 13%(or any number )purge valve command after the car has reached operating temp? mine seems to.(and it keeps higher single digit trim #'s(not sure if this is what is causing this slightly lean condition))

[@kalpitkatpara2720]

Thank you so much for this video. Your explanation is extremely easy to understand and really good.

[@thulanixhulu4674]

Wau!. Great explanation there.My 2jz fse has two valves connected to the canisters. And they both have pipe connectors at the end of the solenoid.the immediately one sucks air through even when not powered and the later one does not. Which of these connectors is connected to the canister which is sucking pressure. Or can u connect them interchangeably?

[@rootney]

Great video I found it very interesting seeing the various systems that she's diagrammed I'm having an issue with a 2000 Ford Taurus. The EVAP test never completes and I think there is an electrical issue with the vent solenoid on my car's system and provide a constant positive 12 volts and when it wants to close the vent solenoid it uses a transistor to pull the negative lead to ground. Now I've tried just connecting the solenoid to an accessory circuit so it's always closed when the car is running but then the ECU to text that there is an issue with the solenoid and presents a fault code. So now what I've resorted to is using an extra solenoid I got from the junkyard just to satisfy the ECU that it has one connected and then the second solenoid the one connected to the charcoal canister will be energized via accessory circuit I know this is a ghetto way to take it but I really need to pass emissions I was wondering if you've ever heard of anything like this before. Also as far as i can tell the intake manafold is connected to the charcoal box with to a diafram valve like ur picture but it has no eletrical conntion it has one vacume line is switched by an electronic pneumatic valve. Ive yet to find a pressurd sensor but there must be one somewhere correct?

[@ajmpatriot4899]

So would a p0456 code be a canister vent or canister itself? Trouble filling tank, pump keeps shutting off due to pressure buildup. Seems like something is clogged not leaking as the code suggests.

[@fieldsofomagh]

Quite an informed video on the evap system and very well presented.

[@rameshmantha1015]

Thank you for a wonderful video on this subject. What led me to your presentation is this. My 2006 Accord 4Cyl auto is showing P2422 error code "Cannister vent valve is stuck closed". I am trying to find out what to do including what parts to replace if any, to resolve this issue.

[@abdullahsaad9340]

Today I work in escalade 2008 , the tank not allowing to refuel , I changed the evap and still the same, then I found out all the pipes contacted to the evap system and the tank are full of small prices of coals . Could you tell me why this happened?

[@georgebushisntcool]

Hey, thanks for the video! What about the vent valve allowing air in so the tank doesnt implode because of the negative pressure when using fuel? Because the gas cap on some car is completely not vented

[@6speeddakota]

I believe I have that incorrect. The vent valve will be commanded open during purge to flush the charcoal canister with fresh air, which will also prevent the tank from vacuuming down.

[@TAO495]

I wish the manufacturer of the EVAP system made the system a little more durable considering the engine performance depends on it so much. My purge valve was stuck open and many tests needed before it was corrected. Thanks for your lecture, very informative.

[@TheBenjammin]

This is a great video, thank you. I'm having a problem that i can't figure out. After refueling, my cars idle stumbles and wants to die for about 30 seconds. After that, it normalizes and runs great until next fill up. No issues putting gas in the tank and No CEL. I've replaced the purge valve and vent valve to No avail. Any suggestions where to look next?

[@ThomasSmith-w8p]

Good info thanks. I have a 2023 mustang GT. Evap system runs at seemingly random times while parked sometimes twice within a few minutes, is this normal?

[@emmcee476]

Normal for a Ford 😅

[@robertramirez1469]

Hello I have a 2007 Chrysler town and country with a 3.3 L. The problem I’m having yes I have a small leak detection also it’s running a bit rough only win engine is warming up and also had to takeoff after that it’s sort of smooth up and runs like it supposed to as I’m running I can hear as though the gas tank is collapsing like loud thump sounds not sure what that is but when I come to a stop and shut the engine off I’ll here allowed squeak Sound I believe coming from the The atmosphere Release vent how can you help not sure what it is

[@RC-Heli835]

Great info man! Thanks for sharing! I had my 1st ever EVAP code P1450 on my Ford Windstar a couple weeks ago and it turns out the line leaving the purge valve to the intake was so dry that it by itself would no longer hold vacuum.

[@endurofan9854]

may i get a clear explanation sir about being dry and not able to hold vacuum?

[@RC-Heli835]

@@endurofan9854 Yes it was a dry rotted hose going into the engine ntake from the fuel tank purge valve under the hood. When the tank would build a little pressure we could smell fuel throughout the car and had to finish a 250 mile trip with the windows down.

[@mr.horse1801]

If monitoring on a ob2 scanner, What should normal vacuum readings be while running?

[@MarzNet256]

Great video. Very concise and well explained.

[@mlez7197]

thank you so much you help me find my problem ...also causing a p0171 and a p0174 lean condition caused by a faulty canister vent valve solenoide...

[@TheAlexBradford]

Good descriptive video. I have a 1 year old car (Subaru Impreza), over the past year it has stalled at least half a dozen times during slow speed acceleration (on hot days after hours of driving). Over the past few months, I've had a noise from the fuel tank area (on hot days after hours of driving). Last month, the workshop finally realised the fuel tank was over pressurising, causing this noise, saying one of the vent lines was kinked, and they fixed it. Well it's happening again/still. What part of this system could I check that would cause the fuel tank to over pressurise? The car is booked to go back into the workshop, but after numerous attempts, I think it's best that I just fix the issue.

[@6speeddakota]

The pressure in the tank and the stalling issue are likely 2 separate issues. It sounds to me almost like the fuel is vapour locking, or somehow you're losing fuel delivery

[@ParulJain2013]

Thank you for this informative video. Maybe I misunderstood, but you said that vent valve is shut during purge. If that is the case from where will the replacement air come into the system? I am learning this tech and know very little, but I think the vent valve should remain open during purge.

[@6speeddakota]

I misspoke, you are correct, the vent opens during purge to flush the canister with fresh air

[@ParulJain2013]

​@@6speeddakotaWhen refueling the vapors in the fuel tank need to go somewhere. The only way vapors can flow into the canister is if the vent valve is open. Also when the car is just sitting, new vapor from fuel in the tank needs to flow into the canister, which again requires the vent valve to be open. This means that the vent valve is always open except for the short duration when the PCM/ECU needs to do a vacuum test of the EVAP system. The vent releases air to the atmosphere when refueling or when new vapor is formed in the tank. It sucks air from atmosphere when purge is operating. When vapor saturated air flows over the charcoal, the charcoal absorbs the vapor, and only air comes out from the vent. When air from vent flows over the charcoal, because the air is unsaturated, it picks up the vapor which is then burnt in the engine. If the car is not driven for long periods of time, it is possible that the charcoal will get saturated from tank vapors. Timely and enough purging is therefore needed for the system to prevent vapor escaping to atmosphere.

[@mustyali9529]

Having a P0455 in A 2006 Acura TSX, replaced the gas cap with an OEM part. It still comes up once in a while like 3 months apart. Thinking of replacing the Vent Valve and Fuel tank pressure sensor. What's your take?

[@ricardoraposo8642]

Hi! Have a question; I have a Toyota FJ cruiser with an auxiliary tank in addition to the original manufacturer tank. Have had this setup for a while (2 years), but recently developed an issue. My tank builds up pressure. When I open the fuel cap, pressure is released. Sounds like quite a bit since sometimes the metal auxiliary tank makes a noise (like it popped back into shape). This also depends on how much I have driven before opening the fuel cap again. But its just a matter of letting the vehicle idle for 10 minutes and pressure builds up and you hear it rush out when opening the cap. No issues while driving (warnings, performance, leaks). I once parked the vehicle for a month after a drive. When I returned, the first thing I did was open the fuel cap (before even turning the vehicle on) and pressure was released like before. So it kept the pressure for all that time. The only thing I can see is that the line running form the canister in the engine bay (which also has a hose coming form the tank and another to the purge valve) to the chassis, is not connected into the chassis frame. Seems the clip broke. Any suggestions?

[@6speeddakota]

So the pressure buildup is most likely from the fuel expanding and creating pressure. When you run the vehicle, the fuel pump in the tank creates heat, thus pressure. All that clip you're referring to does is hold the line to the frame and prevents it from flopping around and getting caught on things. Now I'm not certain how your system is set up, but you definitely need a vent line. This will prevent the fuel tank from getting pressurized, or the opposite, being put under such a vacuum that the pump cannot pull a vacuum. This is actually a common issue on marine engines because the fuel pumps are generally not in the fuel tank and the salt from the water will generally plug up the vent and cause this. I digress; I'm not sure what tank is causing you the issue, whether it be the auxiliary or the factory tank. But it sounds to me like the vent is plugged either way. For the auxiliary fuel tank, if it's a typical racing fuel cell, it will usually have a few ports; one of them is the fuel supply, the other is the return (if used) and the last one is usually a vent. For a lot of racing and off road applications, there's a check valve screwed into the vent port known as a rollover vent. This will prevent fuel from leaking out of the vent if the vehicle were ever to get flipped over. Since it's an FJ, I'm assuming it's probably been off road its fair share of times, it could potentially be that the line to the fuel vent could be plugged up with mud or dirt, or the check valve might be stuck from dirt getting jammed in it. For the factory tank, it should be set up similar to the diagrams in the video. If there's pressure in the tank, try remove the hose that goes into the purge valve on the fuel tank side and it should release all the pressure. If it doesn't and removing the cap does, then it's most likely that something in the charcoal canister has gotten plugged up. Either way, I'd be willing to bet something is plugged on the atmosphere side of the vent valve, again likely from off roading. I've even heard of spiders making nests in the evap vent line before the purge valve. Never encountered that one myself, nor do I particularly want to. Let me know what you figure out, hope this helps.

[@ricardoraposo8642]

@@6speeddakota Thanks a mil for the attention! Also for a great video that helped my understanding. You're right that this vehicle is for off-road. It's only for overlanding and has had a lot of dirt road under it. The auxiliary tank is from frontrunner. I will have a look at these points you made. Thanks again!

[@vunvunoffroad5692]

Thanks for the video, but I have a question. When the vent valve is open, why the fuel vapor does not escape, and only air escapes?

[@6speeddakota]

The fuel vapour is absorbed by the charcoal, that’s why only air escapes

[@josealfredotorresalvarado7415]

i have a 2007 Peugeot 307 2.0lt. my question is or comment is, my evap canister became unlodged the valve thats connected to it also separated from the canister its self, what can happen to the rest of the system, as in contaminants entering the system and messing things up. is there anything i have to reset?

[@tinkertime614]

For a 3 port vapor canister on an older car if you plug the purge port and only connect the vent line to fuel tank, will the canister still be able to breathe through the air inlet and function ok?

[@6speeddakota]

The canister will get saturated because it’s not being purged. It needs to be purged through the engine to clear out the charcoal inside the canister

[@dom9187]

Hi, I'm getting PO496 code and I've already changed my purge and vent valves along with my charcoal canister. Also have a PO420 code related to the catalytic converter but don't think that has anything to do with it. Any idea what could be the issue? Thanks 14:08 14:08 14:08 14:08 14:08 14:08 14:08 14:08 14:08

[@6speeddakota]

The cat code isn't anything to do with that. Typically it's an issue with the purge valve, but in this case, if that's already been replaced, it could be an issue with the fuel tank pressure sensor not reading correctly. Unfortunately I can't really say unless I can look at it directly

[@dom9187]

@@6speeddakota i already changed the fuel tank pressure sensor since i just changed the fuel pump assembly which has the pressure sensor on it

[@asxcd23]

good video. i have a small doubt, from where does the air enter into the tank when fuel discharge into the engine.

[@6speeddakota]

The vent valve cycles sometimes to allow air to flush the charcoal canister and relieve the vacuum on the system

[@johnholley9465]

Have a 1993 chevy 3500 that was a diesel turn to 7.4 gas trying to vent the tank properly can you help

[@derekmjenkins]

I have a 99 VW Eurovan and when putting gas in the car the pump shuts off constantly. No fault is shown on the dash. Was wondering what this would be indicative of. I think you note this would be a Vent Valve that is stuck closed. But would this mean that no fault code would show on the dash.

[@6speeddakota]

What happened with my wife's Mazda was that the charcoal canister was plugged solid and wasn't letting the air escape from the tank. What you need to do is find the line from the canister to the purge valve, make sure it's clear. Then you need to find the line from the tank to the canister, make sure it's clear. If both are clear, then check the canister. Sometimes the charcoal falls apart inside it and plugs it up really badly.

[@sencanboz2645]

Great lecture but still thinking of the one way check valve in case air still needed to be sucked into the tank. This usually occurs on conditions of driving with empty tank all around so that vacuum exceeds.

[@jacknobles1907]

I have a question: How often and when is the purge EVAP valve energized by the PCM? Is the EVAP system purged upon start up of engine and/ or the system intermittently during car operation? Should there be constant engine vacuum to the purge valve at all times (on engine side of valve). I hooked a vacuum gauge on purge valve port (canister side) and waited for system to purge with car running - never saw any vacuum. I then checked engine side hose connected to purge valve - no vacuum there either. Check engine code for EVAP system keeps appearing....

[@6speeddakota]

The EVAP is commanded by the PCM, usually using a pulsed signal. It usually is only commanded on once the engine reaches operating temperature, it usually holds around the 50% mark during regular driving but that's predetermined by the algorithms written in the PCM software. Since the valve controls the vacuum into the purge system, there is always vacuum to on the engine side as far as I know. So you may have either a plugged up or rotten vacuum hose that's causing issues to your purge valve.

[@jacknobles1907]

Thanks for the info - I have a 1997 Isuzu 4 cyl engine. The vacuum hose runs from the purge valve up to underneath engine intake manifold. All I can do is feel hose with fingers - it sorta disappears under manifold. Seems to maybe connect to another solenoid operated device - not sure. I reckon I would have to remove intake manifold along with the mess of hoses and wires to see actually how it functions (lots of work.... drats!) I've come to learn this particular vehicle, Rodeo, has issues with decaying hoses within this manifold so have to take apart to understand it all. Your video was very helpful and informative - thanks for posting it!

[@mb013962]

I have the p2422 code on my civic hybrid meaning that the vent valve is stuck closed. However, I have no issues refueling the vehicle. I’ve also noticed a decrease in gas mileage. The decreased gas mileage may be because of the p0420 code that I also have. Do you think the vent valve might not have an issue?

[@6speeddakota]

what P2422 means is that the computer isn't seeing a change in pressure en the vent valve is opened. So it very well could be that your vent valve is fine, but there may be an issue in the tank pressure sensor. P0420 is a catalyst deficiency code. It'll have nothing to do with fuel economy, but if the cat is plugged, then it'll definitely cause problems and the vehicle will lack power. When is the last time you had a tune up done? If you're not sure, try putting in some new spark plugs and that may be part of the issue.

[@michaelm6045]

Well, scion xb 2006 gives several codes at ones, P043E, P043F, P2401, P2402, P2419. Purge Valve is fine, wires to canister looks ok. I am going to test pump and Vent Valve by applying 12v (to see if them click). Just may be for some experience guy the combination of those five code gives a better idea, please let me know. Good video, thanks.

[@orangejuice4332]

We notice a raw gas smell at warm engine start. I replaced the injector o-rings hoping this was the issue. It wasn't. We do not have any engine codes set. I deliberately left the gas cap loose for 2 days and still no engine codes were set. Any ideas?

[@6speeddakota]

It's very unlikely to be an evap problem in my opinion. If you go to start it and it seems like it starts very rough at first, and/or accompanied by a long crank time, I'd probably head in the direction of an injector that's dribbling once it's shut off. Check the connection between the exhaust manifold and the head, also check the connection between the manifold and the cat. Look at the exhaust anywhere before the catalytic converter. That will generally smell like gas if you have an exhaust leak on the pre-cat side of the exhaust, but you may not notice it as much once it warms up a bit and seals. Lastly, if the vehicle uses a return style fuel injection system, check the fuel pressure regulator to make sure it's not leaking. The ethanol in the fuel will tend to eat through the rubber diaphragm, and cause fuel to leak into the vacuum hose that's connected to it.

[@rohitgurung1677]

When engine is running and during purging fuel vapours enters the intake manifold. Wouldn't it make the air fuel mixture rich? Or even this fumes are taken into account by the ECU.

[@TheLazydavid]

If the vent valve is always open, some gas vapour will leak into atmosphere from the canister. Is there a check valve(ball) so the vapour will not leak to atmosphere and only outside air can be sucked in?

[@6speeddakota]

TheLazydavid it can’t leak fuel vapour into the atmosphere because the charcoal in the canister absorbs it. It’s surprisingly effective.

[@TheLazydavid]

@@6speeddakota Thanks for your explanation! 😄

[@AnythingEverythingGh]

The best video I have watched on this subject. Keep it up Thanks

[@SmudgyContent]

So I just pulled mine off to test it now it’s closed isn’t it supposed to be open when u pull it off?

[@Funz_23_]

I have a 1993 toyota pick up 4 cylinder manuel transmission that just didnt pass the smog check because of the evap fault. Do u have any solutions to this problem?

[@6speeddakota]

You need to determine the cause of the fault. There's a lot of different things that can result in that. You need to narrow it down first.

[@Funz_23_]

I'm going to replace the purge valve n the canister. Let's see if that works. Thanks

[@andrewpeterkin4510]

Can a faulty evap system cause the following: Engine cold, car is started and driven for 10 to 15 minutes. Then, stop at store, shut off engine, return to the car after 15 minutes, start the car but it runs rough, with no power and dies. I then have to wait about 20 minutes before I can start it and drive normally again. I have had it to two different mechanics, and they can't figure it out. Many parts have been replaced, to no avail. Any suggestions. This is on a 1990 Volvo 760 GLE with the V6 engine.

[@6speeddakota]

It's very unlikely an evap system will cause that kind of issue. One thing I've seen cause this type of issue is the coolant temperature sensor being bad. If it thinks it's really cold, it will overfuel the engine, resulting in poor performance or just plain not running at all. The problem is that it can be hard to diagnose with an OBD1 vehicle because the data readouts aren't that great. I'm not super familiar with European cars, so unfortunately I'm not exactly sure what's wrong.

[@andrewpeterkin4510]

@@6speeddakota I did check the temperature sensor. It is one component, but contains two resistors that varies with temperature. One resistor connects to the Ignition System computer and the other to the Fuel System computer. But thanks for responding.

[@bollpl1961ify]

I overhauled my gas tank but now I have fuel spilling at the carbon canister under thermal conditions whether the engine is off or running at temperature..the only way to prevent it is to loosen the gas filler cap...any input is welcome!!

[@corywilliamsmith]

I currently have issues with high pressure in gas tank after driving and my pressure sensor is throwing low and high code. Is this symptom of bad pressure sensor, vent valve, or possibly Canister?

[@6speeddakota]

It's unlikely that the sensor is no good. There's most likely a restriction somewhere between the tank and the vent valve. Sometimes the end of the tube that the vent valve is attached to can get plugged up. What I would do is make sure that the line coming from the canister to the vent valve is not plugged up. If it is, then check if the vent valve is stuck. If it is, you've found your culprit. If the vent valve isn't stuck and the end of the line is free and air flows through it well, then check the charcoal canister to make sure it isn't plugged. I've had that happen on my wife's car. Generally what is indicative of a stuck or plugged vent is that it is hard to put gas in because the air won't vent out of the tank easily when filling it.

[@corywilliamsmith]

@@6speeddakota yeah my hose from valve Solenoid to Canister is clear. Also my charcoal canister is clear. It's weird that it seems as if I am getting symptoms of stuck closed vent valve when it's brand new. I also tested it before I installed it. I do have an aftermarket wire harness so maybe it's wired backwards. I may need a tool to test it though dang it.

[@nickamber8103]

Hey 6speed., this was a very informative video, thanks. I had one question. On my 2004 Tacoma I found the line going from the fuel tank to the canister switch is slightly pinched, could this be causing my truck to stall randomly while driving, also stalls while idling?

[@6speeddakota]

That shouldn't cause any issue, maybe an insufficient flow code but unlikely to cause a stalling issue. I would start by scanning for codes, there are a bunch of different sensors that can cause intermittent stalling including the MAF sensor, crank and cam position sensor, etc.

[@ArtemKobets-b2e]

My question is about gross leak test. So if the purge valve is open and vent valve is closed then vacuum leak can be beyond evap system itself? Thank u

[@6speeddakota]

What will happen is during the leak test is it will open the purge valve until a certain set limit is reached, then it'll close the purge valve and it'll watch the fuel tank pressure sensor to see if there's any decay of the vacuum in the system. If there is, or there's a fluctuation, it'll trip the code. I've also seen a gross leak code get set from the purge valve being stuck open because the pressure sensor will see variations in the pressure readings when they should remain fairly constant

[@tombanes]

I have a 2006 dodge magnum that appears to use the older style NVLD system. I recently got a P0455 (large evap leak) code set 118 secs after a cold start up. From anyones experience , is it common for the vent valve sensor to go bad/ stuck and show a code as if there is a leak when there is not? Tank is at 50% in a heated garage . Thanks

[@6speeddakota]

It can cause a large leak code if the valve is good electrically but stuck mechanically. Most likely there's a split hose or a broken line somewhere, but if that search is fruitless, then you could try energizing the vent valve on the bench using 12v and see if it clicks.

[@tombanes]

@@6speeddakota thanks for the quick reply. Since it was so sensitive I thought it may get stuck mechanically as you said. The car only has 50k on it , kept in a heated garage since 2009 in NYC. I drive it only 1000 miles per year these past 3 years. It is perfectly clean underneath, no oil , dirt or grime. I found it hard to believe the hoses and pipes on the system would rot and split like most cars used daily and exposed to the elements. Maybe there is dry rot due to its age. Thanks for your video and help.

[@handydaddy4232]

My 2002 4-cyliner Toyota Camry smells like raw gas near the tank usually upon shut off. No check engine light. Any ideas?

[@6speeddakota]

It could be a lot of different things, check the fuel cap gasket to make sure it's not ripped and check the hoses coming from the tank to the canister, vent valve, etc. My wife's car smells a bit when the tank is full and it's never given me any issues. It also may be the gasket for the top of the fuel tank where the pump meets the fuel tank.

[@Okie-Tom]

I do have a question. Your diagram shows where vapors from the fuel tank go through charcoal canister where all the vapors are removed from the air before it is vented out the open vent valve. But, then, when the purge valve opens and the vent valve is open, since the vent valve is on the purge valve side of the canister, air would be drawn in the vent and through the piping to the purge valve without sucking through the charcoal canister it appears! I would think the fuel tank cap would be sealed so the system could do an evap vacuum test on the system. So can you tell me how the vapors in the canister can get to the purge valve? I must be missing some little something here. Thanks for the video. Tom

[@6speeddakota]

It's just a lousy drawing of the diagram. There's 3 ports on the charcoal canister, the vent, purge, and feed to the tank. The way the airflow is routed through the canister, the fuel side passes over the charcoal before it gets to the vent, what will happen during purge is the vent will open (I mispoke the way it actually works during the video) and the purge will open flushing fresh air through the canister over the charcoal. The airflow through the canister will pull the vapours out of the charcoal and into the engine. You are correct, the fuel cap is sealed not only for the self testing, but also so the fuel cannot evapourate out of the tank

[@Okie-Tom]

6speeddakota , thanks for the clarification! Three ports makes more sense now. I suppose it is like having internal baffles to direct where each port gets its air! Thanks, Tom

[@chopchoppancake86]

I have a 04 corvette with bad fuel smell it's not throwing any codes has a new gas cap what would be some of the first things I should check I have to leave the garage door open until gas oder clears

[@6speeddakota]

When do you notice the smell? Once it's been driven and parked? or after it's sat for a while? Also, is it hard to start (long crank time) after it's cooled off?

[@chopchoppancake86]

After driven and parked very easy starting

[@6speeddakota]

kzbin.info/www/bejne/fXmsqIVmZ5hmo8U www.corvetteforum.com/forums/c5-tech/2501305-gas-smell-98-c5.html I found a TSB on a forum explaining a very common fuel leak on this exact year, as well as a video of how to fix it. Another place these commonly leak from is the o-ring seals on the fuel line quick connects that connect to the filter. I hope this helps. Good luck and let me know how it goes; I love corvettes, they're some of my favourite cars, I've gotten to drive a C7 ZO6 and it was an experience I'll never forget. I hope to own one in the future, but it has to have 3 pedals ;)

[@chopchoppancake86]

Thank you for the info I'll read though it if you think of anything more please let me know thanks again

[@JRudd]

I didn't expect to see thermodynamics material, that was a pleasant surprise!

[@abdulbakiali4694]

Hi , my ECM says Fuels sensor B is faulty. Which one is (B) driver side or passenger side ?

[@markmshockey1769]

if it failed the gross test i think that would mean that either the purge valve did not open or the vent valve did not close presuming the that the lines are good; do you agree? For the small leak fail i would think either the purge valve did not close or the vent valve did not close presuming good lines; do you agree? Does the small leak use the engine to establish the vacuum? You mentioned a leak detection pump but i would ask which is the most common (e.g. my 2008 santa fe)? It takes a while (days) to get to evap system ready so i am assuming that it uses engine vacuum rather than a pump but am not sure. Is this pump common? For the last item a vacuum switch i wonder how common that is as well. You mentioned Chrysler so am not sure that mine uses that but I have used pressure triggered indirect valves and this seems similar. Obviously i am trying to debug and fix a small leak detected because i can not pass inspection and looking for easy stuff to fix before tracing a bunch of line. Thanks foe the great video!

[@6speeddakota]

You're definitely on the right track. Small leaks can be virtually impossible to find and that can be the single most frustrating thing to look for. It's simply the rate of vacuum decay that the system is looking for, a fast decay will be a gross leak, a slow decay will be a slow leak. A lot of EVAP system monitors require a specific drive cycle in order for the system to set the monitor, so that is one thing you need to investigate is what type of parameters are needed to set the monitor. With a small leak, a lot of the time, the purge or the vent valve doesn't seal quite right, causing it to leak down. Realfixesrealfast had a really good video on this. Generally if you have a line crack or break, it'll usually end up as a gross leak. Easiest thing to do is to check the purge and vent valve first. Easiest way to do that is to locate the purge valve, take the tank side line off, unplug the connector to the valve, start the engine and stick your finger on the port where the hose goes into. If you feel the suction building, you've found your problem. Another way to test it is to take it right out, and either put a vacuum pump on it to see if it'll hold vacuum, or simply try sucking through it. Do the same thing for the vent valve, it wouldn't surprise me if one of them was no good.

[@kucookucoo1]

in the fume purging process, does the EVAP need to draw in fresh air?

[@6speeddakota]

Yes, I was incorrect. As the system purges, it cycles the vent valve to flush the canister with fresh air

[@marks7352]

I have a po442 small evap leak. I have done a smoke test and all is good. I shut the solenoid off while doing the test then I opened the solenoid and the smoke would come out so I do believe my system is silled. However, I hooked my smoke to the brake booster hose and smoke came out around my intake gasket and also a pcv hose , would this set off the code po442 small evap leak?

[@6speeddakota]

It would not set off the evap system leak codes because it's only measuring the pressure after the purge valve. Small leaks can be extremely difficult to pinpoint as they may be so small that it's difficult to see smoke coming out. Scannerdanner has a good video on pinpointing small leaks.

[@marks7352]

@@6speeddakota Thanks...... I wonder if the pcm is telling the solenoid to close?... But then that would say a large leak I'm guessing. Thanks again and probably time to get a new scanner to be able to turn things on and off

[@joshuasmith1215]

So does the vent valve open at all while the fuel pump is sending fuel? I would think it would need to so that air can get into the tank to take up the volume of fuel that is displaced. Because if air couldn't get in while fuel was being delivered, wouldn't that create a very strong vacuum in the fuel tank which would require incredible power to the fuel pump? Or am I understanding something wrong?

[@joshuasmith1215]

Nevermind..."HOW THE EVAPORATIVE EMISSION CONTROL SYSTEM WORKS Sealing the fuel tank is not as simple as it sounds. For one thing, a fuel tank must have some type of venting so air can enter to replace fuel as the fuel is sucked up the fuel pump and sent to the engine. If the tank were sealed tight, the fuel pump would soon create enough negative suction pressure inside the tank to collapse the tank. On older EVAP systems, the tank is vented by a spring-loaded valve inside the gas cap. On newer vehicles, it is vented through the EVAP canister."

[@6speeddakota]

I made an incorrect statement, the vent valve is generally closed for leak testing only, not all the time

[@jacob-no4tf]

@@6speeddakota @Joshua Smith Great explanation. I had this question till I watch this video and coments. Thanks a lot.

[@jacob-no4tf]

@@joshuasmith1215 And also what I think, I found is that those system witch not monitering the EVAP pressure, dont use vent valve. If its not rigth, plz correct me.

[@Dolphin_Teeth]

So would running ur car as u fuel up potentially saturate ur charcoal canister, Since the vent to atmosphere is closed?

[@6speeddakota]

Creme Fraiche you’d have a hell of a time trying to fill the car up, probably because it’ll freak out when the tank pressure sensor reads atmosphere and will cycle the different valves to figure out what’s going on. In that time because the vent will be closed, it won’t allow the air to escape so it’ll travel up the fuel hose and it’ll click the pump off constantly. My wife’s Mazda had a similar situation with a plugged canister and putting gas in it was a real chore

[@Dolphin_Teeth]

@@6speeddakota ok thanks for the response. Great video!

[@spelunkerd]

What an excellent review, thank you, I'm sub'd! There was one point you made at about 5:50 that is in conflict with another video I watched describing the process of purging. I don't know anything about these systems, so my question is innocently asked. It would seem more effective to purge by opening the purge valve and opening the vent valve, so that you are flushing the charcoal with clean air. If the vent valve were closed during purging there would be no way for air to replace the volume of gasses drawn into the throttle body, so the system would quickly develop a vacuum and not move much air. Are you sure the vent valve is closed during a purge? Perhaps it is a multistage process to allow both to happen in sequence?

[@6speeddakota]

I noticed that I blundered that one, I'll have to fix it later on. Thanks for the advice!

[@spelunkerd]

Thank you for clarifying that. Even with a minor glitch, this is one of the best videos I've found describing the way the system works.

[@VideoNOLA]

Note, too, that you cannot pull a "complete" vacuum over a volume of volatile liquid (like gasoline), since under lower pressure more of the fuel will evaporate into -- you guessed it -- gas. In this sense, the system maintains its own equilibrium, desaturating the charcoal without the need for (much) added air.

[@robertrukidding3055]

@@VideoNOLA Partially true, but it would still develop a vacuum without question. No way that evaporation can keep up with steady intake pull.

[@rogjackson]

So the vent valve is open during the purge phase?

[@2dazetake]

Very helpful video, simple explanation with diagrams are the best, thanks so much,subscribed 😊👍

[@jeffjuliebrown8615]

Sometimes I smell gas when I get outside my 07 dodge caravan especially early in the morning after I’ve driven a couple minutes. Thinking vent value may be sticking open from time to time. Also have a “gas cap”msg on my odometer sometimes. What say you? Thx.

[@6speeddakota]

It's unlikely to be the vent valve since the vent valve is after the canister, which will absorb any fuel vapors. It could be anything really from a rotten hose, to a bad seal at the fuel tank where the pump sits in the tank. The easiest way to find an issue is to try smoke testing it. You should be able to find a cheap smoke machine, or make one simply.

[@HORNET6]

I removed the charcoal canister from my motorcycle, is there a probability that doing this will this throw up a fault?

[@6speeddakota]

If it’s fuel injected, it’ll probably throw the check engine, but won’t likely cause any drivability issues as long as the vacuum lines are properly capped. If it’s carbureted, it definitely won’t cause any issues except you need to make sure the vacuum lines are capped so it doesn’t run lean

[@therealgalaxy009]

I replace my fuel tank and my fuel pump and when I turn it on now liquid fuel come spilling out of the EVAP vent valve canister why is that? And the vehicle is never running it just once I turn to the on position that is when fuel comes leaking out of the vent valve canister all over the ground below.

[@6speeddakota]

Sounds to me like you’ve got the lines hooked up wrong. When you turn the key on, the fuel pump primes to pressure up the fuel system, hence why it’s spilling out when you turn the key on.

[@carlifegarage2340]

Hello. This video helped me so much. Only one question remains: when the purge vale opens, how does it draw sufficient fuel vapors when it is also creating a vacuum (since the vent valve is closed). Wouldn’t it help if the vent valve opened to allow sufficient air flow until the canister is correctly purged? It just seems like if a vacuum is being polled not all of the fuel vapor is able to be drawn out. Please let me know. Thanks.

[@carlifegarage2340]

Never mind. I just saw the response to Josh Smith. The vent valve is only closed during the vacuum test.

[@6speeddakota]

I made a mistake, the PCM actually cycles the vent valve open to flush the purge canister with fresh air and allows the fuel vapours to be pulled into the intake. That was totally an oversight and I apologize for that.

[@josephsessaph.d.3575]

I appreciate the logical flow and explanation. I just cannot understand how a 200 Sante Fe 3.5 keeps lighting an evap leak and all but the symptom or problem experienced is if the tank is filled comply and not overfilled the engine at times will not start right away or if it does it takes about a mile for the engine to run at normal RPM. No mechanic has isolated and the only code is the Evap small leak. I have just changed everything except the canister because I did a test as stated by others and the tank pressure valve is original since the tank needs to be dropped to access. Your thoughts? Thx

[@6speeddakota]

A small leak can be very hard to chase, the best thing to do is to take it to someone who can put a smoke machine on it. The smoke machine has a flowmeter and you can crimp off rubber lines one by one until you see the flowmeter drop off, then you can look for the smoke to pinpoint the issue. Small leaks are brutal to find and unfortunately they can be costly with diagnosis.

[@5519663124]

I'm from México , Thanks for the video , do you know if is it normal to have a 20% reading from the evap purge valve on the scan while vehicule idleing ? When vehicule is switch off valve closes normaly it seem to work good when car is moving presing accel valve opens and once reléase accel valve closes to 0%, but when stoping the car completely valve opens an stay at 20%. I getting negative LTFT, once the car reaches high temperature (27% negative ) but befor it, i get around 7% negative LTFT all the time. Any addvice is apreciated.

[@6speeddakota]

20% is fairly normal at a low speed. A negative fuel trim means that the computer is pulling fuel away. This means that the PCM senses rich; this can be the result of a few different things, but it's usually down to 2 culprits. One is that it's getting fuel from an external source somehow, the other is a problem with the oxygen sensor. Since you have the capability to read data on the computer, what you need to do is to check for the function of the oxygen sensor. Once the vehicle warms up, it goes into closed loop and uses the oxygen sensor as a feedback loop, that may explain why the fuel trims shoot way negative when it's warm. So what you need to do is warm the engine up until the loop status shows closed, then look at the oxygen sensor readouts. You're looking at sensor 1, not sensor 2. You should see the volts moving back and forth from near zero, to just below 1 volt. It may not in your case because your fuel trim is pegged all the way negative. So what you need to do is to pull off a major vacuum line like the brake booster hose, and then watch the O2 sensor readout, it should go lean (low volts). Then, take off the intake track and feed it some propane or brake cleaner, be careful not to damage the mass airflow sensor, that will force the engine to run rich. You should see close to 1 volt on the O2 sensor. If you don't see a change in volts by forcing the o2 sensor rich and lean, you have a bad oxygen sensor. If you do see a change, then you've got fuel coming in from an external source. Older vehicles with a return style fuel injection system can have the fuel pressure regulator diaphragm go bad and it will start leaking fuel into the vacuum lines. Another one I've seen before is with a newer direct injection engine, the high pressure fuel pump was leaking gasoline into the engine oil and the fuel was evaporating out of the oil and being sucked into the PCV system. An easy way to determine this is to take the oil cap off and sniff inside the engine, if it smells like gas, there's your culprit. Another way to test is to drain the oil out and smell it for fuel. This doesn't normally happen with a regular MPFI engine though. Let me know what you figure out.

[@5519663124]

@@6speeddakota Thank you for promt response, I remember a mechanic some 7 month ago put an used o2 sensor and my trim reach 2 or 3 % negative , but somebody told me tu clean that o2 sensor whit gasoline and some vineager and i do so , do you think it could be the cause??

[@mrkazanecki1]

@@6speeddakota Thanks for making this video. I needed to understand this stuff. Like Mr Ayala I see 20-35% Does that mean that the purge is slightly opened or that it is cycling opened and closed per minute? And what if the ECM needs to open at 100% to get tank pressure down?

[@6speeddakota]

​@@mrkazanecki1 what is happening is the PCM is sending a pulse width modulated (PWM) signal to the purge solenoid to open it. Applying less than 100% duty cycle will partially open the valve. Basically what they're trying not to do is suck down a bunch of fuel vapour at once, because that'll cause the system to want to correct for a rich condition. Imagine it as sipping on a beer, rather than shotgunning it; at the end, you've still drank all the beer, it's just taken a little longer, but your body isn't going to try compensate because you didn't gulp it all down in one go.

[@tallgiraffelady]

I have a p0440 code on my engine. Do evap codes actually cause problems in the performance of my vehicle? Or is it more for environmental awareness?

[@6speeddakota]

P0440 is evap system general failure, the EVAP system keeps the fuel vapours out of the atmosphere. They shouldn't have much bearing on performance

[@tallgiraffelady]

6speeddakota Thank you

[@sfields004]

Hey 6Speed! I have been plagued with a possible evap problem that I thought was other powertrain components and I am getting closer to understanding the evap system and this problem. It started one hot day and has got progressively worse to where the truck will start losing power and if you try to give it gas it just wants to stall/ drop rpm, if I let off it comes back in rpm's, as I continue under those conditions it Dies. If I let it sit for a few minute or hours it drive fine, If I let it sit overnight it runs great again. Lately since it has gotten cold it does not have any problems until the temperature gets back up to 50 degrees F, then it starts acting up again. Truck is a 2001 s10 4.3L 2 wheel drive automatic. Trouble codes are: current: P0128, P0341, P0440, P0449, P0453. Your thoughts would be helpful, course of action check out Vent Valve? Any help would be great Thank you!!

[@6speeddakota]

P0128 is just a thermostat, easy fix. P0341 is cam position sensor out of range, which means that the signal doesn't correlate to the pulses of the crank sensor, which could mean 3 things; you may have a bad cam sensor, the timing chain may have jumped a tooth, or the distributor isn't in correctly. P0440 is general EVAP system fault, P0449 relates to the vent valve solenoid circuit, so either the coil in the valve is toast or the wiring to it is. Finally P0453 is EVAP pressure sensor high input. Your stalling issues are most likely unrelated to the EVAP faults. First thing to look at is that P0341, that'll definitely cause some issues with the engine trying to run properly. The second thing to check once it starts doing it again is the fuel pump pressure. The lousy central sequential port injection on these engines requires a minimum of 50 psi to pop the nozzles open, so once the fuel pump starts getting weak, these symptoms start appearing.

[@andrewdobbs6615]

Hi on my renault clio 1.2 petrol [2014] I've got a fault p0444 evaporative emission system purge control valve open. I had a vac hose from inlet manifold split to purge valve. Replaced that. I have replaced purge valve and it's still coming up with same fault. I've reset ecu but still can't work out what's going on.

[@6speeddakota]

check to make sure your wiring integrity is good, it should have a signal wire that tells the PCM how far the valve is open or closed, there may be a short or open in that wire. A bi-directional control dealer level scan tool is required here to do the proper diagnosis so you can command the purge valve open and see how far the valve is opening.

[@andrewdobbs6615]

6speeddakota ok thanks it's going to main dealer Thursday so hopefully they can sort it out.

[@kathylewis7543]

I'm going crazy smoke test showed nothing pt cruiser 2005 non turbo touring replaced OME gas cap, purge solenoid and leak detector pump... Still have a P0457 I'm in NY and it won't pass inspection soon!!! Help!!! Some say it could be the filter before the leak detector pump and the hose going to it. I'm throwing one part after another and mechanic scratching his head!!

[@6speeddakota]

Check the vent valve. If it’s stuck open mechanically it’ll definitely trip the gas cap code. Electronically it may still function, which won’t trip a trouble code for it

[@kathylewis7543]

@@6speeddakota thank you

[@waynemincemoyer6458]

Hi. HELP. Have a 64 Buick Special w/ highly modified 455 installed. Strong fuel smell after shutting down from a cruise. Have tried several things with the vent line to eliminate this and nothing has worked. Remembered the two line canister from an 80's car we had and thought if I installed one of those it would eliminate the fuel smell. Ran a line from tank to canister, canister teed into PCV valve line. Seems to help, BUT now there is an extreme amount of pressure in fuel tank??? Don't know what to do from here and it seems like I'm the only person ever to experience this problem. I've talked to other owners of similar vehicles and no one admits to this problem?

[@6speeddakota]

Ok, running the canister to the PCV is a very bad idea, you could end up with serious fuel contamination in the oil. You need to use something called a thermal vacuum switch that threads into the coolant passage in the intake manifold, once the coolant heats up, it'll open up the vacuum passage. Put one end to a vacuum source, its own independent vacuum source, and the other end to the canister. No matter what, you're going to get a fuel smell since the carburetor bowl is vented to the atmosphere. Since our modern ethanol fuels are very volatile, it'll boil the fuel out of the carburetor bowl and create that smell.

[@waynemincemoyer6458]

Thanks. I'm going to Spring Carlisle today(Car flea market & vendors) here in PA. I have Auto Meter gauges so I have two additional questions. Do I replace temp sending unit or use the other port that is available and just install additional thermal vacuum switch w/o wiring to the gauge?

[@6speeddakota]

use the other port. Don't remove the temp sending unit. The TVS has no wiring, it's purely mechanical.

[@waynemincemoyer6458]

Thank You very much.The best to you and your lovely Bride. My Bride and I have been married for 38 years.

[@ganeshvaidyanathan5675]

My doubt is during the purging operation you specified that the canister vent valve is closed which leads to vacuum due to which the fuel is adsorbed from canister what governs the maximum vacuum. How is the amount of fuel going from the charcoal canister controlled. it might sound ridiculous but is the vent valve really closed during the purging operation because what i felt was the due to vacuum the air would be sucked through vent valve which would pick up the fuel from charcoal canister but is this happening or what is really happening during purging is only the fuel getting adsorbed no air please help to clarify my doubts..

[@6speeddakota]

The vent valve is closed during operation. Back in the day, there was nothing that governed the vacuum to the tank. Nowadays, the PCM can control how much the purge valve opens, which controls the level of vacuum into the system.

[@Ruhrstahl1400]

Can you explain how a 2-way valve works in the EVAP system of Honda/Acura?

[@Hector-444]

Is it normal if the vent valve (normally open) is closed when the engine is off? I have a Toyota RAV4 01.

[@6speeddakota]

It shouldn't be unless it has an NVLD system, which is common on chrysler vehicles. If you're having trouble putting gas in it, then I'd say your vent valve is either stuck closed, or the end is plugged somewhere

[@SlowKok]

So, I have an idle issue after refueling. My engine dip in idle rpm for about a couple of seconds after startup, but only straight after refueling. Not otherwise. Have I gotten it straight if I say that my vent valve eventually is stuck in closed mode?

[@6speeddakota]

That seems very odd. I doubt it's the vent valve. If it refuels properly, it won't be the vent valve being stuck closed. I would be more inclined to say it's most likely from the vehicle being shut off and restarted again in a short timeframe. it's probably stumbling when going from open loop operation to closed loop operation. What's the year make and model?

[@SlowKok]

Well.. it's a Volvo V70 1998. The thing is that it has been standing in my parking lot for 6 months. When I started it for the first time a couple of month ago, there was a loud continous ticking sound coming from the canister. It stopped ticking after a few weeks of driving.

[@kidnolan6860]

My 2000 Silverado 1500 wont take any fuel. I pull the vent that connected to the canister and fuel was running out there. I need help

[@6speeddakota]

You've probably got a charcoal canister full of fuel likely from overfilling it, that's my best guess

[@littlebeargaming8267]

I have always known that the vent valve is closed during evap system test and never during purging. Are all system the same?

[@6speeddakota]

I'm sure it varies system by system, each manufacturer has a different way to program the subroutines on their purge cycles

[@hermanrogers1325]

So with all the evap junk it’s still vents to the atmosphere and don’t work just a bunch of junk put on a car to make the check engine light come on and then you have to take the car to the dealership so they can make money so

[@MiahDougie1]

After replacing a leaky fuel neck on my tacoma I am still getting a 0440 code. I tried the smoke test thru the green valve but it feels clogged? Any ideas why it feels clogged?

[@6speeddakota]

P0440 is a general evap system failure code. Usually it points to a component failure in the evap system. The problem is that a P0440 can be very hard to pinpoint because it's a generic code. Which valve is the green valve?

[@MiahDougie1]

6speeddakota the green test port valve

[@6speeddakota]

At rest, with the vehicle off, the vent valve shouldn't be energized and you should have smoke coming out of it like crazy. Try disconnect the hose to the vent valve and see if the smoke comes out; if it does, the valve is stuck closed.

[@MiahDougie1]

6speeddakota after testing again the valve is stuck. Can I unstick it? Or do I need to bye the whole canister ?

[@6speeddakota]

You can try unstick it, maybe a bit of spray lubricant with a little coaxing may free it

[@oldtimedrumcorps]

02 chevy Venture van. Fuel tank was replaced (cracked filler neck at tank) with used tank. New fuel pump AM installed which contains incorporated pressure sensor as OEM . Canister vent solinoid was used from replacement tank , not from original leaking tank Mil light is on 446 code, tank has very high pressure when releasing gas cap ,whoosing and difficult to fill w gas . Just got back original vent solinoid and will swap . Can blow through original vent solinoid with no restrictions No whooshing sound if cap is not tightened . But Im sure code will set if that cap is not clicked down . Will try orig vent valve . whats your take? Thank you

[@6speeddakota]

my wife's car has the same problem. It turns out that the charcoal canister is plugged up. What I did was I tried blowing through each of the hoses until I found where the restriction was

[@oldtimedrumcorps]

Do you know if canister and solinoid can be serviced( removed) without dropping fuel tank or must tank be at least partially dropped (front strap) ? To access solinoid which is directly behind canister on front step ledge of fuel tank. This is vehicle make yr specific 02 chevy venture LS 112 wb . Did you blow the canister out successfully or did you need a new one ? I have heard of compressed air throught he appropriate canister port could work . BTW Canister looks to be possibly removable with out dropping tank . Maybe ?? Regards

[@6speeddakota]

I've never worked on a chevy venture, so I can't tell you but it's worth a shot trying to pull it without pulling the fuel tank. Just pull the line off the vent valve going to the canister, and disconnect the line from the canister to the fuel tank, blow through the the line going to the canister, if it's hard to blow through, your canister is plugged. I tried to blow the canister out and it worked a bit, but hasn't fixed the problem completely.

[@oldtimedrumcorps]

Thanks again

[@Mr.FixItHMS]

So my cars pirge solinoild was bad i replaced it cleared the fault. I can heat my purge valve opening a closing while im at idle and driving a 25 mph. Ive replaces the gas cap as well. I need help.

[@6speeddakota]

What's the code you're getting?

[@3618baqer]

Hi. I am getting P0441fault in my Honda Accord 2017 saying purge malfunction. The same time it gives another fault P04F1 saying low purge flow detected. After watching your video, i opine that my purge valve is not opening or there might be some clogged hose. Can you please advise. Thanks

[@6speeddakota]

For a 2017, I would take it to the dealership because it's most likely under warranty I would assume. Anyway, there's a whole ton of things that could cause an issue like that from a bad purge valve to a bad gas cap. best thing to do would be to use a smoke machine to smoke test the evap system.

[@pingpong9656]

It finally makes sense - well done teacher!

[@sudangang2486]

Thanks for vid can I take these valves out and apply 12 or some volts on each to see if they are stuck close or open. also how many volts I should apply

[@6speeddakota]

Some only use a 5 volt signal. Measure the output before you go ahead and try applying power to things. Be very careful applying power to things, it's super easy to cook the computer if you don't know what you're doing

[@alfredkabura]

Thanks for the explanation a and training Im a life long learner and I'm happy to learn from you and I will keep on learning life makes me want to learn even more .

[@cartertrefz6528]

My dealership is telling me my evap canister is plugged and I need to replace it before it wrecks the catilatic converter. Is this bs?

[@6speeddakota]

I cannot see how the charcoal canister would wreck the converter. Cats get plugged up from excessive unburned fuel, i.e. a misfire, or excessive oil burning. A plugged charcoal canister will make it extremely difficult to put gas in though. That's what happened on my wife's car

[@ntme9]

This is great info but unfortunately it doesn't apply to a 2010 Jeep Wrangler as the canister vent valve is not electro mechanically operated. It's not a solenoid valve. It's just a plunger that creates contact with a continuity switch. I'd love an explanation of how this system would work if the canister event valve was a simple switch as it is with a 2008 through 2010 Jeep Wrangler.

[@mrsemifixit]

Any ideas on a 98 civic with tank side code p1456 that will not be set if ambient temperature is above 70f? Code comes on mostly in colder seasons. Replaced filler neck, cap, bypass and 2-way valve with no difference

[@6speeddakota]

Look at the lines going to and coming from the tank, you've most likely got a rotten line, or it also could be the seal ring around the fuel pump

[@multimicky90]

Won't the small leak cause gross leak as well ? If purge valve is open and vent valve is closed the leak could be in Charcoal canister or intake valve area. Compare to this when purge valve and vent valve both are closed the leak can only be in Charcoal canister. This means if there is no gross leak there cannot be any small leak. Please correct me if I am missing something.

[@6speeddakota]

The difference between a gross leak and small leak is just the time it takes for the vacuum to leak down. The leak could be anywhere between the purge valve to the vent valve, that includes all the fuel tank, all of the fuel lines and hoses as well

[@cherylanntranfagliaflores3883]

hi I have a question my husband truck has this problem.my questions is is it possible that his truck is leaking carbon monoxide or some other Gas? because I bin dizzy and sick since this has stared please get back 2 me thanks

[@6speeddakota]

If there's an exhaust leak and the exhaust is getting into the cab, then absolutely. Sickness, headache, and dizziness are the symptoms of carbon monoxide poisoning.

[@cherylanntranfagliaflores3883]

thank you so much I bin in and out of hospital and thay could not find anything wrong with me

[@MarzNet256]

Cherylann tf It could be and exhaust leak. Get a Carbon Monoxide detector and keep it in the cab (if alarm goes off shut off vehicle and exit at once). It could also be fuel vapors. Keep windows down and get vehicle checked ASAP.

[@mreno1222]

Thank you very much for this! you explained this very easy to understand. Keep up the good work. I'm subbing now.