Jeep JK EVAP system leak? P0455 Try this first!

[chrismanster]

Thanks for doing the video but I have a few things to point out for all the DiYers watching, and this is just my understanding of how it operates, I could be wrong. The pieces you show sliding back and forth inside the ESIM (Evap System Integrity Module) don't move electrically, they operate on pressure alone and small weights in them. The big one is a pressure release and the small one a vacuum release valve (to the passages inside the assembly). Also, there isn't any kind of actuator coil in it, just a diaphragm that pulls in on a contact plate, which is what fails. The connector is just for the contact that tells the ECM if it is working properly. I just changed one on a Charger and cut the old one open to see what the problem was. The diaphragm pulls in when there is vacuum on the tank, so it opens the contact (or possibly closes it), apparently the contact gets dirty or fretting on it so it won't make good contact. I ohm'd the one I took apart and if I pressed firmly on the contact, it would complete the circuit. I don't think the diaphragm can push that hard on it. Just a cheap design. Good thing they aren't expensive. Desert Explorer 302, cut it open at the seam and you'll see how the contact is made (cheaply). You are correct that the plastic lines on the EVAP system split, crack and break because they are made from the crappiest plastic possible. I wouldn't advise applying 12v to the ESIM (self check integrity module), if it's closed contact it's going straight through and could melt your test leads. Probably just melt the wire inside it but I wouldn't test it. Ohm it out, if anything.

[macktaylor]

Thanks for the info, I need to get under mine and check the gas tank lines to figure out my issue. The last part you talked about right next to the battery is the evap purge valve, just fyi.

[benjaminwaters]

7:20 is the purge solenoid, there's two in the system that one in front and the piece on the back, on top of the gas tank, the piece you said has a tendency to break is the rear one. On the JK that can only be replaced with the whole tank. Thanks for the video, I've been dealing with a small leak for some time, replaced just about all components except tank and one last hose I'm ordering soon..

[hillcountrylivin]

Very informative. I've got the P0440 error code on my '09 Wrangler. I've changed out the gas cap and the ESIM on the canister. I'm thinking it may be the fuel tank pressure sensor, but I'm going to go through and check all of the EVAP lines now. Thanks for the suggestion.

[jasonbarnes]

Jeeps used to be simple. Most cars did.

[electrake]

Sorry, I think you got it WRONG and may have thrown out a good device. I believe this pop-off / vacuum valve SHOULD show OPEN CIRCUIT when you are holding this IN HAND. It only contains a diaphragm controlled switch, that I believe shows open circuit when in hand, alternatively, when there is a vacuum applied to the CANISTER port (like when the vehicle is running) of this device, you should see CLOSED connection being made. Gently blowing into the white plastic port (DEVICE OFF THE VEHICLE OBVIOUSLY), WHILE holding the device in the same orientation as when it is mounted - Important!) should also cause the switch to close and make contact. There are TWO sealing shuttles/mechanisms (both gravity driven) inside this device, one to pop-off and vent at an over pressure condition of less than one PSI I believe, and one seal that opens when there is a vacuum pulling to let air into the canister, and if these seals get fouled, the device can fail to maintain some back-pressure or vacuum (which can also be the cause of the code - but not necessarily!). So, OPEN circuit across the two pins when in hand, and CLOSED circuit when there is a VACUUM being applied. This device works in concert with the purge solenoid in front of the battery. Depending on the duty cycle of the solenoid by the battery the system can work to determine if the system is intact (no leaks), has a small leak, or a gross leak. The ECM monitors the contact in the canister valve as it varies the cycling of the purge valve. It is a bit of a dance between these two devices, to ensure the fuel system isn't leaking vapor.

[jviews]

I agree. Check solenoids first, then use a smoke machine. Make it much faster. Do not replace parts which are fine. Thank You.

[Reyrey]

Hi. Can you do a video I’m doing the electrical check on some of them parts ? Any parts are fine. Also what affordable electrical unit do you recommend for us do-it-yourselfers?

[mike-ypuk]

There's no continuity because you have to suck on the large opening to close the the switch.

[ntme]

What would happen if you bypassed the canister, vented straight to the filter/vent behind the tail light and left the canister integrity valve/switch unplugged?

[marcm]

hey i have a 17 wrangler, no codes but it stinks at all times of raw gas.. any ideas?

[HenryV_]

Did your P0455 code said (large leak)?