Need help! Small evap leak giving me fits!

Okay, I've been driving around with my check engine light on due to a small evap leak for months now. I've changed the gas cap. That solved the problem for a week, then the light came back on. I've checked the vacuum hoses for leaks, examined the fuel lines for cracks or splits. I even changed the filler hose and return hose on my gas tank. I can't seem to isolate this leak! Does anyone have any suggestions on where to look next? Is there some type of tool or device that can detect where the leak is coming from? I've checked the other threads, and pretty much have tried everything. The last thing I want to do bring my Jeep to the dealership and get charged to have it isolated. Any suggestions would be greatly appreciated considering my Jeep's inspection ran out 2 months ago.

What code are you getting? What year is the Jeep? I bet the original problem was not a gas cap. Sometimes it can take a while to re-trip the CEL. My 01 did the same thing. I ended up having a very small (4mm) crack in a rubber hose. I doubt it's anything major. You are more than likely looking for a minor crack in a rubber hose. Not a vaccum line but something coming off the evap. canister or connecting the hard fuel lines together. Look at them closely. They run along the drivers frame rail. I replaced about 3 of the 4" sections of rubber hose in that area with new line b/c they were dry rotted and split. There's more of them along the firewall, under the large wiring harness. Good luck.

riverfever said:

What code are you getting? What year is the Jeep? I bet the original problem was not a gas cap. Sometimes it can take a while to re-trip the CEL. My 01 did the same thing. I ended up having a very small (4mm) crack in a rubber hose. I doubt it's anything major. You are more than likely looking for a minor crack in a rubber hose. Not a vaccum line but something coming off the evap. canister or connecting the hard fuel lines together. Look at them closely. They run along the drivers frame rail. I replaced about 3 of the 4" sections of rubber hose in that area with new line b/c they were dry rotted and split. There's more of them along the firewall, under the large wiring harness. Good luck.

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Thanks for the quick reply. I've been tearing my hair out and spending a great deal of time with my Jeep with this problem. The code came up P0456 on my 2000 XJ. I'll take a look at the lines running along the drivers rail again. Maybe I just need a more powerful flashlight or my vision is going! Would you, or anyone else reading this thread, have any pics showing where your leaks were?

Also, does anyone know why the new gas cap caused my Jeep's computer to remove the check engine light after the next cycle, only to have it reappear a week later (and, presumably, with the following cycle)?

Can't answer the question about the gas cap.

I didn't take any pictures of the sections of hose I replaced. I think there were 3 sections of hose that come off the evap. canister. Inspect them very closely. I used a small mirror in order to see all the way around them. They did not appear to be dry rotted but I finally found a small cut on one of them. 3 months later I got a code for a major leak.

There are quite a few rubber connecting hoses that bridge the hard lines together along that frame rail. There's also one against the firewall right behind the motor that was difficult to get to. There's a few more on the passenger side of the engine bay near the solenoid. I'd put a cold one on at least one of these lines being cracked.

Some check engine codes reset on the next start, some take several 'cycles' to clear, depends on the code.

Another good example of the utility of this forum.
My 01 has had the 0456 and 0457 codes for several months now. Check what I could. I had just resigned myself to clearing the codes for ever to get the light out. Now I can look into a few new areas.

Though unlikely, you might also want to inspect where the filler neck connects with the gas tank. My '98 came with a crack where these two components meet, which resulted in a gas tank replacement, under warranty of course..... Another clue might be if you smell gas towards the back of your rig. That's how I help the dealer determine what my problem was...

DaffyXJ said:

Another good example of the utility of this forum.
My 01 has had the 0456 and 0457 codes for several months now. Check what I could. I had just resigned myself to clearing the codes for ever to get the light out. Now I can look into a few new areas.

Click to expand...

Out of curiosity, were you able to pass inspection by clearing the codes? Or, have you not had to worry about that yet?