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 !

[@readchp]

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

[@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.

[@YusufFitness]

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

[@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.

[@stevoidyt]

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

[@kalpitkatpara2720]

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

[@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.

[@MarzNet256]

Great video. Very concise and well explained.

[@rogjackson]

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

[@youdroidsgetoffmylawn]

Thanks for the clear and concise video. Doing diagnostic on one now and wanted to make sure I was clear on theory of operation. This was the best one I found.

[@fieldsofomagh]

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

[@JRudd]

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

[@pingpong9656]

It finally makes sense - well done teacher!

[@AnythingEverythingGh]

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

[@dogbyte555]

I found this video informative, and I learned something.

[@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.

[@joeramirez2458]

Great, great, great video, thank you very much, very helpfull.

[@seshachary5580]

very educative. Thank you regards

[@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 .

[@mreno1222]

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

[@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.

[@ruimvp]

Very informative. Thank you for your work.

[@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...

[@OfficialVoy]

Thank you! I hope you and your wife are doing good!

[@beingsentient]

The most informative explanation of EVAP I've found. Question: where is the vent valve usually located. I understand the purge valve is located under the hood, attached to the intake system, which makes it convenient. Many thanks.

[@6speeddakota]

Vent valve is typically either mounted directly to the canister or very near it with a rubber hose to connect the two

[@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.

[@2dazetake]

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

[@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?

[@Blair62]

That was a great video. Thanks.

[@thomson4420]

very clear explanation.

[@bvanderveen]

Awesome explanation! Thank you! Only wish i’d watched before my buddy whose truck wouldn’t fill up right spent $1k on a new gas tank …

[@davidessien5465]

Thank you for sharing these ideas

[@eosborne9w6]

Great content, thanks for this video.

[@TAO495]

Very good lecture. Learned a lot, thxs

[@billlincoln6087]

EXCELLENT EXPLANATIONS.

[@gerardlunow567]

Nice Job. Time to go troubleshoot.

[@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.

[@janinemay9899]

VERY Excellent video!

[@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.

[@blazintrails3023]

100th comment huh? Incredible video it's extremely informative and to the point. Awesome job and thanks this has really helped me understand things

[@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?

[@achiriu1987]

Thank you for the video and thank you guys for the comments.

[@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.

[@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.

[@electricmechanic6420]

You are the best... Thanks

[@michaelmardini346]

excellent video! thanks

[@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?

[@ehabalakrawi6028]

An excellent video

[@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.

[@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?

[@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

[@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))

[@richeobrador1976]

thank you very much

[@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!!

[@nugenki]

Very good video, thanks

[@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?

[@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.

[@cru551010]

thank you man!!!!! very nice video!!!

[@rodolfosandino5369]

Great video!

[@robertrukidding3055]

Cool that they got McLean Stevenson to narrate.

[@davidessien5465]

Your video is nice

[@NasirHussain-wt2si]

Very good explained thank. Need information regarding euro 1 to euro 7 diesel & petrol engines. Please.

[@Herlongian]

The charcoal in the canister is not absorbent. It is adsorbent.

[@geeegeee]

Nicely done.

[@potatosalad9519]

good video, im impressed.

[@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.

[@64impalaSSRealMechanic315]

Great Work Brother

[@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

[@mr.horse1801]

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

[@Ruhrstahl1400]

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

[@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

[@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.

[@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.

[@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?

[@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

[@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.

[@luisalejandrojorquera7896]

excellent review thank you very good

[@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?

[@johnholley9465]

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

[@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.

[@bonkant6584]

Great video. Very clear especially with the diagrams. I have a question though. What would happen if your purge valve was stuck closed? I would assume that the vapors would continue to build up until something happened? Would the vent valve eventually be able to vent the vapors into atmosphere? Again great video!

[@6speeddakota]

What would eventually happen is the charcoal canister would become saturated to the point where fuel vapours cannot be absorbed by the charcoal and will start coming out the vent valve.

[@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.

[@Pertamax7-HD]

nice sir

[@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

[@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.

[@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?

[@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.

[@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

[@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!

[@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.

[@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.

[@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!

[@sumonsbd]

Hi, do you have any idea, why my car fuel leaks from the tank when the tank is full after filling the gas. It leaks significantly until I stop filling the gas. I checked underneath; it is not from the charcoal canister, it’s from the gas tank. My car is nissan x-trail 2005. It is not leaking from filler neck vent though. We smell gas for few days after filling gas.

[@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! 😄

[@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?

[@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.

[@abdulbakiali4694]

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