Check Engine Code Says EVAP How to Diagnose EVAP System Problems and Leaks

In this video, I'm going over some common problems if you have a check engine light with an EVAP issue. So you're driving your car, you have no drivability issues, your check engine light comes on, and you scan it and you either have a large system leak, or a small system leak in the EVAP system. The first thing you wanna check, and I know I say it all the time, is check your gas cap. Make sure it's not loose, grab it, pull it off and check the seal, make sure the seal isn't cracking. Now, most of the time when you have a gas cap leak where it's the seal cracking, you're gonna get a small system leak, not so much a large leak. Also check the filler cap, see if there's any rust buildup. If there's anything rusty there, you're either gonna have to replace that filler neck or you might be able to sand it down with a little bit of sandpaper or Emery cloth, and probably replace the gas cap as well. Make sure that's tight.

Under the hood we have a purge solenoid. What that does is brings vacuum to the EVAP system. You get the vacuum through the intake manifold as the engine's running, and there's an electrical connector attached to the purge valve right there. Now, if these leak, a lot of times you'll get a different type of code, but sometimes you can still get a small leak or large leak code. And in that case, you just got to replace this solenoid. It's pretty easy, just disconnect the hoses, disconnect the connector, put the new one in, you're good to go. Now we're underneath the vehicle and this is actually an extremely simple system to understand, because everything's open. The vacuum line is right here and that goes to the purge solenoid. So when the purge solenoid under the hood opens up, you get vacuum that comes along here, and it goes into this vapor canister.

There's charcoal in this canister, and when the fuel vapors enter this, this is gonna eliminate them from going out into the atmosphere. So vacuum comes into this, and it puts a vacuum on the fuel tank where the vapors are, it goes to the top of the fuel tank, and then it comes out this line over here. This is the EVAP canister vent solenoid, so this is gonna vent off some of that vacuum if there's too much vacuum. And if this is leaking, that's gonna cause a large leak or a small leak. And as you can see, there's actually a crack in the hose right there. And in the solenoid right there, there's a electronically controlled valve and you can see that it's cracked. So that's gonna have to be replaced as well.

There's an electrical connector on this, just two wires that actuate that on and off. So a common problem is these valves getting clogged up or leaking, not just visually. You won't be able to see this all the time. Sometimes it's internal. Debris and sand and other contaminants will get into the valve, and just cause it not to close properly. And that's going to give you a check engine light. So this entire system has to be sealed with the gas tank, the canister, the lines, and even the vent valve. When the system is just sitting, this valve is gonna be open. When it activates, this valve closes and then the front purge solenoid opens, but normally it has to be sealed. If you have a leak, one way they test this system is with a smoke tester. If you don't have a smoke tester you can do the best you can, look for anything obvious like this and that'll probably help you out. A lot of times you can see something on this.

To recap what we just went over, these are the most common problems when you have an EVAP leak, the purge valve, the vent solenoid valve, and also the gas cap. You could have other problems but these are the most common. If you enjoyed this video and it helped you out, make sure you subscribe to our channel, ring that bell, turn on all notifications, so you don't miss any of our videos.