Evap codes (shop smoke test shows no leaks)

rmasteller

rmasteller

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Hi. I have 1 or 2 Evap codes on the simple OBD2 reader. I didn't want to buy a smoke machine and learn how to use it, so I took the Jeep to a shop. They said their smoke test didn't reveal a leak, so they recommended replacing the usual suspects, the canister and the purge valve. I said no, I'll do that myself. Well, I'm coming to the trusted Forum for assistance again for a diagnostic procedure. While a couple suggestions roll in, I'll be over to the side researching and educating myself. Thanks!!
 
macleanflood said:
Which specific codes?

-Mac
Click to expand...

My guess would be small and extra small evap leaks.
I'd be highly surprised if all the rubber vacuum fittings are good along with the stuff on top of the tank. If you aren't carefully watching with some good light, you won't see the smoke in those areas.

I would however, borrow a known good gas cap and start there.
 
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I found testing procedure in service manual. I'm reading through them now. I bought a new gas cap when these codes popped up a couple years ago, no help.
 
rmasteller said:
I found testing procedure in service manual. I'm reading through them now. I bought a new gas cap when these codes popped up a couple years ago, no help.
Click to expand...
I just dealt with one. I could clearly see smoke coming out of the gas cap during the smoke test. Later after I stopped the test, I removed the gas cap to check something else and it was holding pressure or vacuum. Somehow the pressure from the smoke test made whatever mechanism they use to seal the cap functional again.

In other words, take nothing for granted. If you think something is good, verify it before you trust it.
 
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My 05 just periodically throws a small evap leak code. I tried a few gas caps and eventually just started clearing the code and going about my business until the next one popped up. Just another facet of Jeep life.
 
On my ‘99 the “large leak” code kept resurfacing. Smoke test showed everything was tight. It turned out to be the purge solenoid. I went through THREE of them before get one working solenoid. Code hasn’t been back for several months.
 
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any4xx said:
On my ‘99 the “large leak” code kept resurfacing. Smoke test showed everything was tight. It turned out to be the purge solenoid. I went through THREE of them before get one working solenoid. Code hasn’t been back for several months.
Click to expand...

Brand of the one that worked? Or did you just go for the best "one out of four" with the same Chinese brand? :unsure:
 
TheBoogieman said:
Brand of the one that worked? Or did you just go for the best "one out of four" with the same Chinese brand? :unsure:
Click to expand...

I think the one that finally worked was a Dorman. But of the two defective ones, one of those was also a Dorman. The other was (maybe) SMP?
 
I bought a new gas cap directly from Jeep, even though my aftermarket locking car's seal is very soft. Cleared codes and am driving as often as I can to see if codes return.
 
moabrubi said:
Sorry, let me be more specific for you..

Where exactly in the service manual did you locate the testing procedure? I read through the section regarding EVAP however could not find any testing procedures.
Click to expand...

https://wranglertjforum.com/attachments/2006-tj-powertrain-pdf.14050/

Sorry, it was in powertrain document. It gives a description of all the OBD codes and what to do about them. Search your code.

Now, of course I've gotten sidetracked from my issue. I bought & installed the new cap, drove a number of times for however many miles, and eventually the check engine light and the codes came back on. Haven't moved on to next step. Independent shop could not get smoke to come out anywhere, recommended replacing a couple random "best guess" parts. Dealership said smoke test would cost $300!!!! I'd buy a tool and do it myself, but I'm not sure I would do it well, having no experience. I feel kind of stuck.
 
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rmasteller said:
https://wranglertjforum.com/attachments/2006-tj-powertrain-pdf.14050/

Sorry, it was in powertrain document. It gives a description of all the OBD codes and what to do about them. Search your code.

Now, of course I've gotten sidetracked from my issue. I bought & installed the new cap, drove a number of times for however many miles, and eventually the check engine light and the codes came back on. Haven't moved on to next step. Independent shop could not get smoke to come out anywhere, recommended replacing a couple random "best guess" parts. Dealership said smoke test would cost $300!!!! I'd buy a tool and do it myself, but I'm not sure I would do it well, having no experience. I feel kind of stuck.
Click to expand...

I bought a smoke tester from the jungle vendor last year for about $80.00.
 

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