Diagnosis + Understanding EVAP Systems (SBQM Full Video)

[@JH-bh5lm]

For years I've been a victim of unskilled mechanics and I'm sick of that. Now I have started learning about car diagnostic and repair work my self. I'm happy to have come across your channel because in my country there is no school to learn these things from. Many thanks from Sarayevo, Bosnia & Herzegovina.

[@ramoutarramjit9018]

Thanks solve my hesitation rough idle an stalling on accelerate l am from Trinidad mechanics don't know about evap system

[@johnsoper7649]

The quality and quality of information here meets and exceeds the wildest expectations of anybody who wants to learn and grow

[@vinniechacon3853]

Man .. Respect for giving people from developing countries the pass. That speaks to me on the kind a man you are .

[@andrewyear81]

It most certainly does speak on the gentleman's character. I know this comment is a year old but as you can see, kindness is an easy gift that just keeps on giving. I'm probably going to go premium on his pay site just because of that selfless act. Ofcourse the free info I've been getting and the promise of more may have something to do with it too.

[@pacojuanrico]

Developing countries? Man you're brainwashed

[@beemerkon]

Always the Americans having to pay

[@SchrodingersBox]

That’s because Americans have more opportunity than almost any other country. In America, ANYONE who works exceptionally hard, gets educated, stays out of trouble with the law, acts professional and makes good decisions will be successful. ANYONE. In other countries that’s not always true. But soon it won’t be true in America either, as a lot of people who don’t have the discipline to be successful want to ruin it for everyone.

[@JoseVazquez-jy9vq]

@@SchrodingersBox hi I'm jose from mexico, I wonder if you can give access, I love cars, but here in mexico is very very expensive to take your car to get fixed, so I love to do it myself. Thank you. I fascinated with you videos!!

[@andrewyear81]

We should all feel very lucky to have a man like you as an ambassador to our craft. Thank you kind sir .

[@SchrodingersBox]

What a compliment!! Thank you!!

[@enhancedphysique6452]

Ever met Scotty Kilmer ? #1

[@dougirvin2413]

Give a man a fish and you feed him for a day, teach a man to fish and he's never hungry again. Great vids Matt, keep up the good work.

[@SchrodingersBox]

I always add “Pray he gets a fish and he will starve to death waiting for a fish”

[@johnengland8619]

give a man a fish. feed him for a day. teach a man to fish and then he wants to drink beer on his boat all day

[@itsourenity]

@@SchrodingersBox Build a man a fire, keep him warm for a night. Set a man on fire, KEEP HIM WARM FOR THE REST OF HIS LIFE!

[@hectorcontreras6356]

give a man a fish and you feed him for a day. teach a man to use an oscilloscope and he will never change plugs and wires under faulty assumptions again!

[@chuckiec20]

Unless of course you then tax him heavily.

[@alexxicotli7665]

My dad is a Mechanic, and has always wanted me to learn things on my own. He pretty much trouble shoots and has me take the parts off. Now I'm a recovering from being a replacement parts only type of person, now with great Teacher. I'm a troubleshooter of my own. I been watching your videos and I paid to subscribed on your website. Thanks Matt! I wished I would of seen your videos before I tried to trouble shoot an old 1994 Acura. Spend so much money replacing censors. You ask why my dad didn't help me? Well that was supposed to be my Learning Car. Never got it to run smooth. But when I saw your videos I realized what was causing the car to stutter. I have the basics understand that the car needs gas, electricity, and air. But never down to the nitty-gritty. Again, Thanks for sharing and caring Matt.

[@josesilva-if4uv]

Hello Matt, I really enjoy your lectures. You are a good teacher and explain things very well. I never had the money or opportunity as a teenager to learn any trade. Ive loved cars all my life.. I never settled to learn or be an expert for a trade in life, but Ive decided to learn about cars about 3 years ago, the problem was that I am a 40 plus year old person and felt uncomfortable with kids that could be my sons in class with me. I saw a couple of them even laughing at me. That alone made me just quit going to school here at my local community college.. The Adult school auto tech classes are slow learning and the only accept you within their registration time frame. The whole government school system could use an overhaul. Put better classes and faster curriculoms. I takes forever to learn with them. You are one of the best teacher here on youtube. Thank you

[@SchrodingersBox]

Thank you!!!

[@TheEgg185]

College is DISGUSTING. In addition to other things, I hate the slow 4 year pace to complete the education. That's great if you're a kid. But an adult wants to get that piece of paper and start earning money ASAP. A summer break is a slap in the face to most adults.

[@RedEyedJedi]

You left because some kids laughed at you?

[@dylanisaacs16]

Just wanted to say you have done more for me more than years of being "professionally" taught. Thank you Sir

[@SchrodingersBox]

Oh wow good to know!! Thanks for putting the time in on your end to make it worth while!!

[@RayRay-ov7uw]

The paid channel is like getting a college education for $3.50 a month. If just one of Matt's videos helps you, you will have saved enough money to pay his subscription for 3 years. Thanks for all the hours you put in behind the scenes Matt

[@xVoidCypher]

id pay!

[@charlemagnecv7135]

How do you enroll?

[@cswango1714]

What you do is very noble and honest for the less fortunate! Very thoughtful, you are an asset to the world. Be safe friend!

[@smartchishaya1670]

Brother you are great ,this is a real lesson great teacher love from Zimbabwe

[@jacobdonnell2443]

God bless you, I need my car, and I am older, 57, I needed a simple view of the EVAP system. Thanks. Jacob Donnell Fort Worth, Texas.

[@VopiscusGuitar]

I appreciate your making the distinction between pressurized and vacuumized systems. Other videos were very unclear on that point, mentioning both phenomena by turns as if they occurred simultaneously, which was tying my brain in knots. Thanks for the lesson dude

[@SchrodingersBox]

You are welcome!

[@TheJoefussGarage]

Hello there, I'm a Tech consultant for HVAC, though have loved cars since childhood.. Dad and uncle trained since then, mostly on classics and antiques.. I work on my own current modern cars as well.. I learned so much in one of your EVAP segments. You are quite the Gentleman and and scholar.. Thank you for the resources you provide to all, if we are willing to just listen 👂.. God bless..

[@SchrodingersBox]

Much appreciated!!!

[@themechanic6117]

I'm on his paid channel and it really is worth it. He makes what seems to be complicated systems like this one and breaks it down into easy to understand videos just as he did in this video. There's so much value there for the little that he charges and there's plenty of videos already up to keep you busy learning !

[@DENicholsAutoBravado]

And if you forget something remember it's available as reference! Great use of a slow day at work.

[@themechanic6117]

@@DENicholsAutoBravado that's true

[@beautybyhammerllc]

I work with many immigrants and they're so easy to teach . They want to learn . You're a good man !

[@salvadornunez5829]

you are a great,human being!!!thank you for your teachings,this is the era where any body can share their knowledge to the world thank you again!!!God bless.

[@TRG972]

My college degree is in automotive technology, with factory training, and years of experience in advanced driveability diagnosis. I hope your viewers know that the content shared in your videos is at least matched, or better than what many automotive programs charge tuition fees for. You are way ahead most other "automotive educators" on here. I'm impressed! For anyone considering the paid subscription, I can assure you that it's well worth getting this level of information. Thanks for the theory refresher.

[@SchrodingersBox]

Thanks man!!

[@or1g1n4l01]

Videos such as these make me regret going to school for auto tech.

[@xavierchesang5995]

Hi, i've read manuals about evap system but i have never gotten a crystal clear understanding until today thanks man. Watching from Mogadishu in Somalia.

[@SuperMarioDiagnostics]

Well explained. Kudos for mentioning the pump. Something most techs don't know about. The pump itself is another potential leak source. Great explanation! Very cool that your giving free access to those in developing countries. 😎 That's something you don't see every day. 👍

[@DENicholsAutoBravado]

Yeah. When I first ran into a pump I was like WHAT!? Truth be told I didn't know it pumped it up. I assumed vacuum still. Lol

[@SuperMarioDiagnostics]

DE Nichols yup. First time i saw it, i was looking at a diagram, and it said leak detection pump, and did a double take lol did some digging and good to go.

[@tollfree7322]

Hello DIY, how do you diagnose a heated thermostat

[@SuperMarioDiagnostics]

😒Troll free?

[@jagjeetraien3448]

oh & bless your heart man!!! you a real one , thankyou for looking out for people in developing countries , it makes me so happy to see people being so caring and genuine ! BLESS!!!!

[@csj2640]

These are amazing videos. I usually just kept replacing parts until I fixed it. I just saw your fuel pressure video and was like , I should of had a Matt 8 video. Thank you professor Matt. Your videos are clear and answer a lot of questions. Thanks again and keep them coming.

[@SchrodingersBox]

Great to hear! Yes for those who are willing to learn- diagnosis is way better than the parts cannon!!!

[@joselopezgarcia528]

That is exactly what I do, at the end I end up replacing good parts and wasting hard earned money

[@pbierre]

The EVAP system plays a significant role during refueling. Here, it pays to call out the 2 generations of EVAP design: (pre-2006): OBVR (On-board vapor recovery): The gas pump is a 1-channel delivery device, delivering gasoline, and the vehicle has to manage venting while containing fumes. Venting takes place via the (passively open) Vent Solenoid Valve with most fumes absorbed into the charcoal canister. post-2006 EVR Phase 2 (Enhanced Vapor Recovery - California standard). The gas pump is a 2-channel device, pumping gas into the filler neck, and suctioning vapors in the reverse direction back underground into the reservoir. (You'll notice a tiny 3mm orifice on the pump nozzle). EVR Phase 2 vehicles have a Refueling Vent Pipe going directly from the apex of the tank back up to the filler throat. Some brands (e.g. Volvo) have a dust filter where the Vent Pipe "T"s into the filler throat, and it can become clogged over time with residue -- this will cause difficult refueling where the pump shuts off prematurely. If an OBVR vehicle is difficult to refuel at a EVR Phase 2 gas station, it is because its vent path (thru the float valve, Canister and Vent Valve) is being blocked. Without adequate venting, the flow rate of gasoline into the tank is deceased by air fighting its way back up the filler pipe. Think of the way water "chugs" out of an inverted soda container "glug, glug, glug", compared to the smooth, rapid flow if you poke a vent hole. If gas is flowing out the gas pump nozzle faster than the tank can receive it, the liquid level in the filler pipe backs up rapidly, and wham...the gas pump thinks the tank is full.

[@lancemartin9221]

Best evap video hands down. For once i feel confident in diagnosing/understanding evap systems.

[@PatriciaOhnstad]

Simple, to the point. I have watched quite a few of these explanations, but this is the first one that was very clear. When I saw the whiteboard, I just about passed it up. That would have been a BIG mistake.

[@OldtimerMercedesBenz]

Another wonderful video. Even though I know these systems, I still like to listen to your explanation. I wish you would be my professor back in the days! Keep up the good work for people who want to learn and for those, who don't have the privilege of learning this in school. Thank you!

[@Madasin_Paine]

High quality instruction. Well edited to be comprehensive without wasting too much time.

[@SchrodingersBox]

Thank you!

[@kiddbrother3]

FYI the evap test port Schrader valve (left-hand thread) should be removed if using to test with a smoke machine will restrict the flow!

[@shmeehoe37]

Yeah I found that out the hard way LOL

[@thecardoc100]

I glanced through the comments and didn't see where anyone mentioned the leak detection pump strategies. Toyota does use a pressure sensor with their leak detection pump system, it's inside the pump assembly and they use vacuum for testing. The leak detection pump found on Mazda, Hyundai/Kia, BMW and some others does not use a pressure sensor. In order to test they pressurize the system and measure the current that the pump motor draws. They start by pumping air through a .020" orifice and storing the current value that the pump was drawing for a reference.(Example: 22mA) Then when they switch over for the actual test, the pump current drops at first as the air starts to pressurize the cannister and tank. As the pressure increases, the current drawn by the pump increases. During the test, if the amperage drawn falls well short of the reference current (5mA) then it is judged to be a large leak, slightly below the reference current is a small leak. (20mA) If the current exceeds the reference then the system passes the test. (26mA)

[@sinegra30]

Hi! Thank you for posting this videos! You just master the way of teaching to make it so easy to understand! I've learned fuel trims with your videos among some other important things! I live in Dominican Republic we share the island with Haiti in the caribbean, as you mentioned before there are no schools or any technical institutions around here to learn Automotive mechanics...I have been struggling looking for information and tutorials to learn and make a living around here from this profession, I am very interested in your offer about a membership for your most detailed teachings, thank you for the opportunity!

[@mikestyles1035]

Since I started watching your videos I'm way less stupid then I used to be. Thanks

[@ChristmasCrustacean1]

I liked as soon as you said you will give free membership to anyone from developing nations and the third world

[@FuelAirSparkTime]

Wait .. Where's my white privilege?

[@dronejunkee2743]

Thank you very much for posting this video. I rely upon your videos because I cannot afford schooling and your videos help me in my passion to become an automotive technician.

[@SchrodingersBox]

You're very welcome!

[@InternetDude]

1,000 Scotty Kilmer videos < this one.

[@nickwilson1476]

"rev up your engines....its time to learn nothing!"

[@glendasue70]

I like him.

[@fairfieldholmes9553]

@@glendasue70 As do the 1.6 million subscribers to his channel.

[@rightconditions2010]

@@nickwilson1476 that was funny. Thanks

[@xVoidCypher]

@@nickwilson1476 LOL! scotty is entry level, this is the next step up! Leave scotty alone hes a great motivator!

[@motojaknow2612]

Samuel Clements said "Fortunately my schooling hasn't interfered with my education". My generation grew up with IC engines (I'm 80 years old) so I am in full agreement that engines can't be diagnosed without "thinking", and usually a lot of it. I detect a little bitterness toward "professionals" with an ego. I swore off asking for help long ago following many bad experiences. Fortunately, we now have KZbin with guys like you with great advice. Thank you. But obviously you are not uneducated with a name like Schrodinger's Box, so I'm guessing physics. Now what does the probability of an electron being at a particular location have to do with a bad fuel injector? If you can't afford a Snap On scope, I found a little box called a GTC 505 that is quite nice for quick analysis of ignition systems. It really works.

[@shaunsautorepairs5410]

The only thing that stops me watching more of your videos is there isnt enough hours in my day...

[@armenbagdasarian6144]

great video, 98 camry been throwing codes (evap) after replacing charcoal cannister. Just replaced purge valve. As someone without all the specialized tools I am "shotgunning" the problems then waiting for the system to reset. I learned about idle air control valves from other videos and I have fun learning.

[@phigo4kins]

Nice. Just in time. Been riding around for 3 months with EVAP leak, didn't know Shi*t about how they Operate. Now, I'm gonna go Snake that sucker out like a Boss! Thanks!!

[@donlute3444]

Good job. Even though my vehicle is a 2006 Ford Expedition, this showed me the issue and location of the suspected criminal valve. Well done. And! 5 hours later. The canister and valve is not there! I called the dealership and they said it was above the spare tire. In order to get to( what might be ) the canister takes some dismantling of that area. I'm not having fun.

[@enriquerivera3335]

u do awesome work. hell with the haters.

[@donmoore7785]

This is great. My Volvo has a leak detection pump, and yours is the first explanation of how it works I have seen.

[@SchrodingersBox]

Yes and actually your LDP is a bit unique. i believe Volvos - instead of using pressure sensors in the tank, instead measure the LDP amperage and extrapolate that if there is lower than anticipated amperage for a certain amount of time, this obviously equates to a leak in the system. The reduction in amperage is proportionate to size of the leak.

[@billyyoder8171]

Thank you Matt. Good job. I appreciate your videos. Bless you for helping others around the world.

[@seapoacher]

2007 Subaru Outback with no codes. Hard start especially in cold weather. New battery, plugs and wires didn't fix. Finally changed the the evaporation purge valve. That did it! Thanks for your help! 🙂👍

[@TheCowgirlNiamh]

Just about to go to bed. You can be my bedtime story ☺️ Sweet dreams

[@SchrodingersBox]

Hey when do I get a schrödinger’s cat clock hahaha!! I need two of them so I can keep track of time in superpositional duality.

[@TheCowgirlNiamh]

Well Matt, I'm not sure if duality would apply here but if you can calculate the quantity of wine we would need to consume to make two identical clocks, we would be willing to be your lab rats 😉😂

[@DENicholsAutoBravado]

@@TheCowgirlNiamh you had me at duality then you got me even more.

[@TheCowgirlNiamh]

😂😂😂

[@elir079]

Very universal as far as other vehicles. Helped me understand how the EVAP system works.

[@jensole2617]

Hi Matt... I’m from Denmark and Fox News stated that Denmark is comparable to Venezuela... so does that qualify me for free access to Your paid channel... Jeans

[@SchrodingersBox]

Hahahahaha.....well I might consider giving you free access just for being in Denmark and watching Fox news!

[@milosaleksic1982]

Greeting from Latam, it was the first time I learned about EVAP system, and my perception went from a "complex system with a fancy name" to few vacuum lines.... Awesome, thanks for sharing your knowledge.

[@SchrodingersBox]

Thanks for sharing!

[@InternetDude]

100 Eric the car guy videos < this one.

[@jb6574]

InternetDude you do realize both channels have completely different content. This channel is dedicated in going in depth with engine diagnostic while Eric's is dedicated on showing how to make mechanical repairs. Ones showing the technical side of cars while the other is showing the mechanical nuts and bolts part of a car

[@InternetDude]

that slow goat there’s a reason he’s Eric the car guy and not Eric the mechanic.

[@jb6574]

InternetDude if you're going to compare shrodinger to other car channels compare him to other technical diagnostic channels like scannerdanner, Wells vehicle electronics and other channels..big difference between mechanics and technicians

[@jb6574]

InternetDude also have you done half the repairs that Eric's done yourself or even know how

[@InternetDude]

that slow goat I DIY basically everything and have videos to show for it

[@johnensley4844]

I have a 2012 lincoln mkx with a ez fill gas filler. ( no gas cap) I keep having a bank 2 sensor issue, that is making my car engine shake and run rough. I feel that capless gas filler is the problem. Should I replace the gas filler?

[@SchrodingersBox]

It is not possible the gas cap can cause that. Especially on only one bank. Do a fuel trim analysis to find the issue.

[@johnensley4844]

@@SchrodingersBox thank you for responding. I look into it and get the test done.

[@johnensley4844]

What kind of mechanic should I seek out that would know about fuel trim. My engine code is P0352.

[@SchrodingersBox]

Any competent mechanic should be very familiar with it. It the basic foundation of diagnostics.

[@johnc4352]

Hi Matt, I live in Sullivan County, upstate New York and I would like to claim third world status!

[@SuperMarioDiagnostics]

John C 🤣

[@rustynail9793]

If you live in a democrat ran state, you are basically a 3rd world country...

[@InsideOfMyOwnMind]

Does the PRoKiliforniastan count?

[@johnmack5024]

Mexifornia is no better.

[@JosePerez-bo7vg]

Hi my name is Jose , I really like the way you make everything very simple to understand. I leave in Juarez Mexico where mechanic schools are very outdated would love your help.

[@totiriel6079]

Great info Sir! Same issue with my car. Struggling for months now I have a better understanding. I do really appreciate it.....

[@SchrodingersBox]

Right on!

[@vicecitysociety]

I spend $12 a month for music ima be droppin the money for your knowledge brother very helpful video and great explanation

[@SchrodingersBox]

Rock on! much appreciated!!

[@tracyliedtke6780]

I gladly pay the miniscule amount for your depth of knowledge. Support Matt. Grow the 2%.

[@SchrodingersBox]

Thanks Tracy, yeah I saw you joined yesterday. If you still need help with that car you're working on let me know

[@daleshelley1993]

Can any of this Cause the PCM to drop below 9 V and also give you a gas cap signal even if your gas cap works

[@daleshelley1993]

2006 Ford Mustang 4.0

[@SchrodingersBox]

technically there is no such thing as a “gas cap signal”. The evap monitor can’t tell exactly where a leak is- it can just tell how much of one there is. yes it’s possible a low voltage could case a solenoid to fail to close completely and thus signal a leak.

[@jesi.o1502]

Kudos from Nigeria, I really learnt alot. I will be asking questions from time to time because your channel is very helpful.

[@SchrodingersBox]

Glad to answer them!

[@anthonyelhosri2229]

Best evap video hands down ,many thanks for you

[@SchrodingersBox]

Thank you!!

[@bladimirmeza1424]

Thank you ,your video helped me fixed my Rx 300 evap leak with out tools just following your way of thinking you are much appreciated.unfortunately I replace 2 sensors before I watch your video on one of which needed to be replaced the egr was cracked but the air mass sensor was good and I changed it with out proper testing … oh well now I know. I had a big leak beside the Egr .from now on I’m not changing any part till I use your method it’s the right way .thank you very much

[@MrNickelodion]

Im Working my ears listening your english. You excel the language with your clear pronunciation, but the plus is that im learning so much stuff of mechanic that i never tough to learn, i apreciate your efort on everything you are doing.

[@SchrodingersBox]

Thank you. I have many people from other countries tell me this and I consider it my favorite compliment.

[@michaelfletcher214]

You rock! I'll get my sh*t soon and join for the 3.49 a month. Yes, absolutely worth it. This is my second time watching you explain the operation and diagnosis of a particular system in a modern automobile. The first time I watched your channel I was seeking knock sensor information for my 04 CRV. Of course, I'm still working that.

[@SchrodingersBox]

thanks!!! yes if you like that format where I explain the components and systems you will LOVE the paid content channel because there is much more of that and I explain it even better.

[@jamr2t]

This is off topic, but you mentioned smoke testing. I had a EGR flow code p0400, & decided to smoke test my intake after the purge valve just making sure it wasn’t a chewed up hose somewhere to my EGR or map sensor. Got that taken care of. But I found many leaks, but one I could not wrap my head around was the smoke out of my dipstick. I took care of it & replaced the o-ring but was wondering how smoke leaks out through there? Causing a vacuum leak. It’s a M112 V6 on a MB E320. Thanks for your videos!

[@SchrodingersBox]

PCv is connected to the induction.

[@chriscooper2454]

A NATIONAL FRIGGIN TREASURE!!! THAT'S ALL I CAN SAY,AS I'M SIMPLY IN AWE OF YOUR ABOVE AND BEYOND IN A SIMPLE AND UNDERSTANDIBLE EXPLANATION WITH OUT MAKING A REGULAR GUY FEEL DUMB. TY VERY VERY VERY MUCH.

[@SchrodingersBox]

Thanks for the compliment!!

[@jviews1]

Very good. Had details about the system, now your lesson placed it all together in one understanding.

[@keithdin7337]

I am down in Cape Town, South Africa. Thanks to algorithms cause your channel was suggested plenty times since i have started to slowly transform or switch from a wrench to a bit technical ODB diagnostic DIY mechanic! None of your vids are vague and boring, but highly informative!

[@SchrodingersBox]

Hahaha, the biggest complaint I get is they are "boring and just talk" refreshing to see some intellectual people out there who understand that it is indeed exciting and the case studies are like murder mysteries!!

[@keithdin7337]

@@SchrodingersBox Jeez, google failed to notify me concerning your reply. Though, some folks might be jealous of the fact that you draw thousands of people to your channel and/or to watch your tutorials. Plus your advanced technical prowess and whim! Aha, i remember now - i will have to contact you very soon. Thanking you lots!

[@cristianbivolan708]

Hi Matt, as an old, retired electrical engineer I am very impressed with your teaching skills. Repairing my cars is one of my hobbies, but sometimes I am getting stuck into hidden specific manufacturing problems, like a fuse found under the wax paper insolation on a small AC transformer. Anyhow, I would greatly appreciate if you could help me troubleshoot my 2003 BMW 745Li, which started with not accepting more than 1/2 tank fuel (except when dispensing very, very little at the time), and lately getting the so popular check engine light on with the P0444 code on it. I disconnected and tested the purge valve and seems to be perfectly fine, opening and closing promptly when applying 12v to it. It may be that the purge valve intake hose having a small leak at the connection to the other hose going to the charcoal canister is triggering the P0444 code, but I do not believe this has anything to do with the tank not accepting more than half fuel. BTW, there is no pressure, nor vacuum at the filling cap after driving the car. Could you please feed back with your expertise/experience on this? Thanks a million, Chris

[@legallass9905]

Hey Matt, you missed this comment from Christian.

[@christopherjpresti]

You are a gentleman and scholar. Thanks for the education.

[@inhocsigno9151]

The canister vent solenoid is closed only when the evap system is undergoing a leak check monitor. So when driving down the road the evap vent is open so the purge of gas vapors can occur. Otherwise the engine will just pull vacuum on the system and the charcoal will remain saturated. It's surprising how little air filtration occurs when the outside air enters the system. Might keeps or rocks, but not dust, IMO.

[@SchrodingersBox]

That’s correct.

[@thesetruths1404]

Hi. I have a 1998 3.3L Nissan Pathfinder. 175,000 miles. Great condition. Stock. My tank gets alarmingly pressurized when driven a couple hundred miles. I don't have any codes. My Nissan gas cap visually inspects clean and good. Does not leak. I even disconnected all hoses on the EVAP system and cracked the gas cap. No codes were made either. How can that be? I drove it dozens of miles to test. To see if the missing stopped or codes would appear. No codes, except random misfire. Every now and then, but the motor is obviously missing mildly to badly all the time. It gets worse for a while when I refuel. For a few dozen miles. When this system started doing this, I started getting a random misfire code at the same time. These may be unrelated. Not sure. I have verified purge valve works, hoses are clear now. One was dirty about 2" clogged at the canister for the purge line. It looked like charcoal dust. All other hoses clear. Any ideas? I was going to remove the plug from the cannister ambient vent valve and see what that did. It should toss a code right? And make the valve open, from my understanding? I don't want the tank to pressurize like that again. It will spew and hiss for about 6 minutes when cap is removed. I've never seen a vehicle do it this badly before. Thanks!

[@SchrodingersBox]

You either have a clogged vent from the tank OR the pressure sensor is faulty and not representing the actual pressure which isn’t high. Are you measuring pressure separately or are you using the PID for tank pressure?

[@thesetruths1404]

@@SchrodingersBox there is a plastic threaded port on the evap purge line under the hood. I may have a fuel pressure adapter I could attach there. There is a label on it saying max 1 PSI. I have tried running it many miles with the cap cracked loose. It didn't change any operation or throw a code. PID? My simple Bluetooth obd2 reader is what I'm using. App on phone.

[@SchrodingersBox]

Measure actual pressure. I bet it’s within spec.

[@dyardsale5475]

Very good general explanation which cleared up some knowledge gaps for me.

[@SchrodingersBox]

Glad to hear!!

[@FunnyReaction-m8f]

when part of the gas in tank consumed ,vacuum created in the tank ..air should enter tank to recover this vacuum..from wher this air come ..gas tank cap or solenoid vent valve?

[@pjay3028]

Hi, excellent video, thanks.I have read that when the purge solenoid stops working on my car, it can be impossible to fill the fuel tank with fuel, and or, the car won't start immediately after being filled with fuel because the engine becomes "flooded" with a rich fuel mixture due to excessive fuel vapour. Does this sound likely to be the purge valve? Would the fuel filling issue be when the valve sticks closed and the starting issue be when it sticks open? Thanks again.

[@SchrodingersBox]

sounds way more like a vent solenoid.

[@philtheduck09]

Thank you for taking the time to make this video on the evap system. I've been having trouble getting the evap monitor to run even after replacing the canister and purge solenoid. Completed a smoke test and fixed 2 small leaks. No codes showing yet 100's of miles later and the Evap monitor is still not ready. Driving me completely nuts. Any suggestions? Appreciate any ideas

[@xanny7373]

In your example you say the sensor waits for vacuum, where does the vacuum come from? Is it just engine vacuum? Now i’m wondering if the purge goes before or after the throttle body if it needs vacuum? Also if it does use engine vacuum then would a vacuum leak be able to trip a large leak ?

[@SchrodingersBox]

Good questions. The operation is explained in another video on this channel “diagnosis and understanding Evap systems”

[@OverlyCuriousEngineer]

Excellent presentation. One thing i'm confused about is the function of the evap vent solenoid. If its normally open why doesn't fuel vapor leak out through there? Especially since the sys is already pressurized by fuel vapors?

[@SchrodingersBox]

It's because the charcoal cannister traps the vapors.

[@OverlyCuriousEngineer]

Schrodingers Box so what exactly then, is the function of the vent solenoid? Simply to allow the PCM to do a leak test?

[@SchrodingersBox]

@@OverlyCuriousEngineer Oh yeah sorry- I should have answered that. Twoi funbctions. One is when closing the vent solenoid (an opening purge) it draws in the vapors from the cannister. The second function as you said is to seal the system for the decay rate test.

[@OverlyCuriousEngineer]

So in both cases, the solenoid closes. Correct? Why the need for a solenoid then? Why can’t they just close off this part? I’m sorry I’m still very confused.

[@cdcbeats551]

So I have a 2004 vw Jetta that I’ve had for about 2 years. For about a year now it’s had this constant issue of stalling when below a 1/4 tank. Recently it got worse and started stalling when 1/2 a tank or less. (When it happens the car starts bucking even at 80 mph and will just shut off.) this has me baffled and I’ve put 3 fuel pumps in it, checked all my fuel lines. And even cleaned my gas tank. As well as putting a new fuel filter on. I’ve never gotten a check engine light for this. So two days ago I was checking out my evap lines after putting in my 3rd fuel pump and it still stalling and I was gonna pull off my purge valve to see if it still holds vacuum. Well I unplugged the plug for it and decided to go inside for the day forgetting to plug it back in. (The hoses are still on it. It just no longer has voltage. ) well magically with just it unplugged my car hasn’t stalled since. Can someone please explain this? Is it a problem with the purge valve itself? Or more of a Ecu issue???? This has kept me up at night lol.

[@SchrodingersBox]

Check the impact of the purge line variables on fuel trim. That should give you a solid basic direction to start with.

[@ggua92722]

Hi Matt, great DIY video. Thank you sharing. My 02 Tacoma Prerunner is giving me a fault codes P0440 & P0442 I have a feeling the culprit is the Vent Valve. But I’m not 100% sure which end to connect my vacuum pump to check if it holds vacuum. Is it the end to the canister or to the air filter? Or maybe one of your subscribers know this. Thank you.

[@SchrodingersBox]

doesnt matter- connecting on either end and CLOSING THE VALVE should hold vacuum.

[@jacob-no4tf]

awsome explaination. There is a question, the fuel tank is completely sealed, so how the air comes to fuel tank instead the amount of the fuel wich burned?

[@Heyoootsmario]

I have a question. At about 10:13 You mention the purge is normally closed. Then you say when the the pcm turns off the purge circuit that the purge will then open... Isn’t it the pcm will turn on the purge valve and then the valve will open allowing the intake air to pull vacuum.?

[@SchrodingersBox]

So if I recall, on the GM example, the purge valve is normally closed when energized. De-energizing (turning off the valve" then lets it move to its relaxed state (open).

[@Heyoootsmario]

Ahh yes you’re correct good sir. Thank you for the reply.

[@iamthevanavator281]

Signing up for QM is a no brainer. Tons of valuable content, well worth the monthly subscription. I am a trained and certified aircraft mechanic, I watch a lot of mechanical videos on KZbin, but this channel, FordTech Makuloco, Scanner Danner and Ratchets and Wrenches are my go to’s for sound, technically correct knowledge and procedure for understanding and fixing vehicles,

[@SchrodingersBox]

Thanks man, being included with those great mechanics made my day!

[@charlesgould8436]

I've learned from all of your vids. Some I had to watch many times.

[@doitmyself6377]

Only now I understand this evap system. Thank you!

[@sidallen685]

So did you say that the vent solenoid is normally open? When performing a smoke test would you have to use a scan tool to close the vent solenoid to prevent getting a false test result?

[@SchrodingersBox]

Or just manually close it by applying voltage to the solenoid.

[@sidallen685]

Schrodingers Box Why would it be normally open to the atmosphere, doesn’t that defeat the purpose?

[@SchrodingersBox]

because the charcoal is present to absorb fumes. You don’t want it pressurized so having it open to atmosphere but not releasing vapors is optimal.

[@sidallen685]

Schrodingers Box Thanks for the info, that one had me stumped

[@patrickrobinson317]

Great tutorial. The BEST one I've ever seen on this topic. Thanks !!! 😀 Patrick from Bethesda, Maryland

[@iandrackert7838]

My question is, how does air get into the fuel tank to prevent vacuum as the fuel is used??

[@SchrodingersBox]

Through the evap vent.

[@iandrackert7838]

@@SchrodingersBox thanks for the reply. I have a VW and it's not setting an evap code but after driving for a while, especially in hot temps my fuel pressure drops to the point the car hesitates and I can hear the fuel pump surge. I can also see lean condition when this occurs in the fuel trims. Fuel pump checks out. If I leave the car to sit it works fine again. If I fill it with gas while it's doing it it runs fine for a while. But if it happens for a prolonged time (highway driving for example) it will then not fill with gas. Ive replaced the charcoal canister and made sure no lines have restriction. Purge valve and evap canister valves replaced. This one has me real stumped. Thanks for your great vids!

[@s_alfred8597]

This is a great video.. hope more video like this in the future...i am from malaysia...

[@gothops154]

If you unplug the hose that connects the gas tank to the charcoal evap canister, and you still have problems filling up gas for more than 3-5 seconds at a time, that means the problem must be on the shutoff valve attached to the gas tank, correct?

[@SchrodingersBox]

Correct. Or an obstruction in the actual filler neck like to tank itself.

[@gothops154]

@@SchrodingersBox can I get your opinion on my situation? I just bought a used 2004 Subaru STI with a preexisting condition: 1) the gas only fills up 3-5 seconds at a time 2) check engine light throwing error code: P0457 Subaru Code - EVAP System Leak Detected Fuel Cap Loose/Off The previous owner took it to a mechanic a few times but doesn’t know exactly what was replaced except the fuel cap. But as I said, he took it more than once, so I believe the charcoal canister (looks visually newer than the rest of the underbody) and some other parts were also replaced. HOWEVER, if like I said, I pulled the hose connecting the gas tank to the charcoal canister and it still doesn’t fill up quickly, it doesn’t matter what was or wasn’t replaced bc we know the issue has to be with the shutoff valve on the gas tank or an obstruction in the neck. This also lines up with what the previous owner told me, that his mechanic said the next step would be to drop the tank and replace “some part”. So I think I’m on the right track, however dropping the tank on an 04 STI requires disassembling nearly the entire rear end ($$$) so I want to be extra diligent with my diagnosis. This part on the gas tank is called “Vent Valve” part no. 42084FA161, so I’m a bit concerned it’s not the same as the shutoff valve you’re referring to in the video. But with the symptoms of 1) and 2) I posted above, does it make sense this is the failed part, esp when combining with the pulling the hose off the canister and still being unable to fill up for more than 3-5 seconds at a time? Would that part failing be causing these issues, because to me they almost seem contradicting, if I have a “EVAP System Leak Detected Fuel Cap Loose/Off”, wouldn’t I be able to pump gas without issue? Where as not being able to pump gas seems more like a “blockage” rather than a “leak”, but maybe the error code is a “catch all” code.

[@brianlopez8934]

I truly appreciate your help for additional knowledge sir I hope your still making more videos

[@SchrodingersBox]

I am and in fact I will release a new one on a couple days!!

[@skee0310]

Hands down... you’re an all around stand up guy!! Thank you Matt for all that you do for us.

[@jamesbush4568]

Thats a great description and explanation of the evap system. Do you have a video of testing components to see which one failed to allow fuel from going into gas rank

[@LandUsJustInTime]

Love to here you giving the developing countries the free class your a good man for that I’m not a mechanic however I’m mechanically inclined and your lessons are perfect 👌

[@SchrodingersBox]

thank you!!

[@radunastasa8531]

Thank you for the video! I have one question: When I cold start the car and open the window, I can detect a strong smell of gas. Is it possible that this is gas vapors that released from the EVAP vent? Or there is an issue somewere in the fuel system? Thank you!

[@SchrodingersBox]

Could be that or engine is running excessively rich at startup.

[@xelementzgaming7171]

I have a 2003 Honda Civic.. had the code p1457... I changed, the gas cap, charcoal canister, shut off solenoid, by pass solenoid... and the code still came back on... anything else that it could be? I’m tired of changing parts and still having the code

[@SchrodingersBox]

What data do you have?

[@xelementzgaming7171]

Schrodingers Box what do you mean by data?

[@SchrodingersBox]

@@xelementzgaming7171 I need to see that data you used to determine the parts you changed were suspect. For example you changed the gas cap- how did you determine there was a leak at the gas cap? You changed the bypass solenoid- what was the voltage at the solenoid and was there full voltage drop on the ground when activated? You changed the shutoff solenoid- same thing- what was your voltage and voltage drop measurements to determine the solenoid was the problem? I have to have the basic data to determine where the issue is.

[@xelementzgaming7171]

Schrodingers Box well to be honest this is my first car ever... so when I got the check engine light on.. I went to AutoZone to see what code I got... and it was P1457 EVAP LEAK CANISTER AREA... so I googled it 🙈 and it gave the list of probable cause.. but that’s about it 🙁

[@SchrodingersBox]

lol ok- well unfortunately i can’t help without data. I would have to see that the solenoids are functioning properly by applying voltage to close them and then vacuum testing the lines. . Your best bet is vacuum testing the lines at this point since everything else was changed... but it could be a huge number of things. You have to narrow down to where this issue is and then test the suspected component in where you narrowed down to.

[@bme7491]

I'm still trying to figure out why my 2002 Highlander fills slowly (fuel handle clicks off over and over), when the car has no MLI, no codes, runs fine. Air vent tube is clear. Wondering if the overflow check valve could be stuck closed while not affecting the EVAP monitoring tests.

[@SchrodingersBox]

good thought. sure sounds like a vent tube restriction to me though but if it’s clear I like your idea.

[@xxDADDYDAYCARExx]

Just found your channel due to a Toyota Corolla (2000) MAF or MAP sensor fault ?? Time will tell?? Just wanted to commend you on giving out free access to 3rd world trainees. The world is a little bit better with people like you doing good deeds like that. Well done and best of luck with EVERYTHING YOU DO ❤️🇮🇪❤️🇮🇪❤️🇮🇪👍👍👍👍👍👍👍👍

[@jackxshockz8711]

Hi matt am one those who come from third world countries and i like ur educative videos which have helped me very much in my understanding the working systems of automotive. Much more than I learned in school keep it up and if there is anything u can do to help me be a better mechanic I will appreciate

[@SchrodingersBox]

Happy to help! send me a message with your email and we’ll see about getting you free access to the paid channel.

[@jackxshockz8711]

Thanks in advance. I'll get in touch.

[@foreverwood1963]

Good video ! Theres one thing that I need a clearer understanding on. You stated that if someone is checking the system with smoke that they can misread that the system is leaking through the solenoid because it's open to atmosphere. How is it that the system will allow smoke to leak from it and not fumes? Does it have anything to do with it's molecular weight?

[@SchrodingersBox]

No it's because the charcoal cannister stores the vapors so they are not released to atmosphere.

[@foreverwood1963]

@@SchrodingersBox Thanks

[@GiotheGhreat]

I hear a hissing sound coming from the throttle body. This hose is connected to the back of the throttle body and it looks very brittle and complete squeezed. Is this related to power loss? Thanks for sharing!

[@SchrodingersBox]

What data do you have?

[@kalinradoulov3760]

Nice explanation, just one quick question, what are you testing on green cap service point (pressure, vacuum?thanks again

[@SchrodingersBox]

Yes correct.

[@MrBufordWilson]

Can you explain the evap vent valve. Normally open, it seems like the gasoline fumes would escape from cannister to atmosphere there.

[@SchrodingersBox]

yes it would seem that way however the actual gas vapors are trapped in the charcoal cannister. if there wasn’t a charcoal canister then yes- you would normally smell fuel outside the vehicle since the vent is open.

[@SE45CX]

What I really like about you is your perseverance to reach to a full understanding of tougher topics like this. Great work.

[@richardmueller9565]

I read on another video says P0443 ix evap purge silinoid. Maybe that line is plugged. If unhook that-- tank shouldnt ever get pressized either...something is causing the pressure not allowing fill flipper anti-roll over on the fill hose not to open. sometimes seeps in slow--sometimes totally closed. usually after driven 20+ miles.

[@SchrodingersBox]

Sure that could be one of many many many many possibilities too