2003 Yukon SLT 4 Wheel Drive Evap Issue

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zmann96

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I have a 2003 Yukon SLT 5.3L 4 wheel drive. I've gotten a evap code on my scanner and it specified large leak. I've replace the canister a while back. I got under the truck and checked all the connections from the filler to just before gas tank. it's difficult to check there without dropping the tank. I was wondering if anyone tried pressurizing the system with about 5-10 lbs of air at the gas filler ? I have ordered a cap just to rule that out.
 

Larryjb

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It's good to get the code, and do some diagnosis. However, the purge control valve is a common failure point and is easy to test:

 
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zmann96

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I already replaced the canister or purge valve. I have a large leak somewhere and was wondering if I could find it with air, maybe 5-10 lbs so I can hear it
 

Larryjb

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I do remember hearing from one guy that he found ACDelco purge valves defective from the start. it may be worth checking it to make sure it holds vacuum. I agree though, it's probably something else. Do you know anyone with a smoke machine?
 
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zmann96

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I do remember hearing from one guy that he found ACDelco purge valves defective from the start. it may be worth checking it to make sure it holds vacuum. I agree though, it's probably something else. Do you know anyone with a smoke machine?
No I don't but I know it would be better. I just don't want to ruin any parts with too much pressure
 
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zmann96

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well I sealed my gas filler tube with tape, I put a small hole in it. I used my compressor to introduce air into the filler tube. I didn't hear any leaks. I had a friend do it while I got underneath and still couldn't feel or hear anything other than air going into tank. I created an access cover under my left side passenger seat to make it easier to change fuel pump. I had my friend introduce air again and I felt a leak at the fuel pump seal. I took out the fuel pump and fixed the seal and replaced and finally after introducing air the pressure came out the filler. problem fixed.
 
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