Evap Leak Assistance

[moabrubi]

Hi All,

I'm trying to diagnose a P0440, P0455, P0456 codes that I am getting on my 2005 LJ, I started with the purge valve, which appears to be functioning as it should. Next I hooked up a smoke machine to the line coming out of the bottom of the purge valve (the one that goes back to the tank). All lines seem okay, I am only getting smoke out of the leak detection pump filter (circled below)

I believe this should be normal, correct? Since I am not having any other other leaks, I'm wondering if replacing the leak detection pump would be the next best move. Would a faulty LDP throw small and large evap leak codes?

Thank you for any assistance.

 

[Chris]

Hi All,

I'm trying to diagnose a P0440, P0455, P0456 codes that I am getting on my 2005 LJ, I started with the purge valve, which appears to be functioning as it should. Next I hooked up a smoke machine to the line coming out of the bottom of the purge valve (the one that goes back to the tank). All lines seem okay, I am only getting smoke out of the leak detection pump filter (circled below)

I believe this should be normal, correct? Since I am not having any other other leaks, I'm wondering if replacing the leak detection pump would be the next best move. Would a faulty LDP throw small and large evap leak codes?

Thank you for any assistance.


View attachment 660521

Some smoke escaping from the leak detection pump could be normal, especially if it's a small amount.

If you’ve confirmed that the purge valve is functioning properly and there are no visible leaks in the lines or connections, replacing the LDP could be a good next step. A faulty LDP might not always manifest obvious physical symptoms, but it can definitely lead to the codes you’re seeing (especially if it’s failing to properly detect leaks).

Before you replace it, though, make sure to double-check the gas cap and the condition of the EVAP canister as well. A faulty cap or canister can also trigger these codes. Good luck, and keep us updated on what you find!

 

[moabrubi]

Some smoke escaping from the leak detection pump could be normal, especially if it's a small amount.

If you’ve confirmed that the purge valve is functioning properly and there are no visible leaks in the lines or connections, replacing the LDP could be a good next step. A faulty LDP might not always manifest obvious physical symptoms, but it can definitely lead to the codes you’re seeing (especially if it’s failing to properly detect leaks).

Before you replace it, though, make sure to double-check the gas cap and the condition of the EVAP canister as well. A faulty cap or canister can also trigger these codes. Good luck, and keep us updated on what you find!

Thanks, The gas cap is new so unfortunately i didn't get that lucky. The evap canister from the outside looks OK, no damage or anything. Not sure what other variables there are to look for.

I went ahead and gambled on it being the LDP, i swapped it out today. Fingers crossed that it works.

 

[Chris]

Thanks, The gas cap is new so unfortunately i didn't get that lucky. The evap canister from the outside looks OK, no damage or anything. Not sure what other variables there are to look for.

I went ahead and gambled on it being the LDP, i swapped it out today. Fingers crossed that it works.

Let us know if that solves the issue! Be sure to clear the code after replacing it.

 

[macleanflood]

On my 97 my evap solenoid was full of charcoal from a failed cannister.

-Mac

 

[wayleigh]

Sorry you’re going through this. I was looking everywhere and was glad it was finally the gas cap in my case. Sorry to hear of your chase. Let’s us know!

 

[moabrubi]

Replaced the LDP and have run a few tanks through it now. Seems to be working as it should and no CEL.

Thanks for all the advice, hopefully this helps someone later.

 

[moabrubi]

Guess I celebrated too soon, Now I have a P0452 that won't go away. I replaced the gas cap again just to try but no dice.

I had already smoke tested it back in December when I originally posted it and there was no leaks. I can smoke test it again but doubt that's my issue.

Anywhere else I should look?

 

[WVJeep304]

Guess I celebrated too soon, Now I have a P0452 that won't go away. I replaced the gas cap again just to try but no dice.

I had already smoke tested it back in December when I originally posted it and there was no leaks. I can smoke test it again but doubt that's my issue.

Anywhere else I should look?

When I was fighting this, we found 2 things:
1) I had some holes in my fuel filler neck.
2) one of the plastic fittings on top of the fuel tank was broken.

We replaced the fuel filler neck and fixed the cracked fitting and the code went away. We found both of these on the 4th or 5th smoke test, and barely found them then. The smoke was staying up under the tub from the filler neck and stayed on top of the tank from the fitting. Had we not looked hard with it on the lift, we'd have likely missed it again.

 

[moabrubi]

I smoke tested it again for a good while, double checked those fittings on top of the tank as those broke on a previous Jeep I had, all good there. Also wanted to clarify it's actually a P0457 I'm getting.

The only place i am getting smoke is from the leak detection pump filter from the original post, which i believe is normal. I'm putting smoke in from the bottom hose of the purge valve under the hood, is there anywhere I might be missing?


Super annoying and if I weren't considering selling this Jeep i would've given up and just lived with the light.. LOL.