Evaporative Emissions System
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Laughing Gas
Joined: Nov 2014
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Evaporative Emissions System
OK-I am seriously in over my head on this one. The check engine light has been on a couple of times and it would be a code for a leak. Today I got the P0455 "Evap system leak detected - large leak" The "large leak" was a new one. I have the workshop manual on what things to test. Problem is I don't know where they are and if I did I would not know how to test them. The only other possible clue I have is a period where the "check your fuel cap" would come on. The thing is it did it with a new fuel cap as well as the original. Could there be an issue in the filler tube? I'm just grasping at straws so any suggestions are appreciated. On the good side, there seems to be no effect as far as running or driving = knock on wood
Hotshot
Joined: Jan 2004
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From: St Louis
If you're in over your head, it would be most expedient to take the truck to a shop and have them smoke test the evaporative emissions system. When done by someone who knows what they're doing, this procedure will quickly pinpont the source of any leak.
Either the vent valve isn't closing when commanded or you have a gross leak in the system which could be anything.
The EVAP system is purely for emission control only, it has nothing to do with how the truck drives or operates.
Either the vent valve isn't closing when commanded or you have a gross leak in the system which could be anything.
The EVAP system is purely for emission control only, it has nothing to do with how the truck drives or operates.
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Laughing Gas
Joined: Nov 2014
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Thanks Good to know it won't leave me stranded. I'm still trying to find a place, other than the dealer, to do a number of things. They are capable but the dealer has done things to negate my good faith, so to speak. I'm picking up a purge valve and give it a shot. There seems to be issues with vacuums on this rig. I don't know if it's because it was cooked in the CA sun or if it was a Fri pm or Mon am build.
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An EVAP leak will be an vacuum leak most of the time, if not all the time when running.
Check the lines to and from when you change the purge valve.
If it was a filler hose, you would probably have a fuel leak when full.
Check the lines to and from when you change the purge valve.
If it was a filler hose, you would probably have a fuel leak when full.
Fleet Mechanic
Joined: Mar 2019
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On mine when I had the head off earlier this summer I found the rubber lines going to the charcoal canister and the purge valve to be bad. They didn't look bad but as soon as I touched them they disintegrated.
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I'm currently waiting on a purge valve I ordered. Through some troubleshooting I was to the point where I suspected there was something wrong with the purge valve. I pulled it off to test it tonight. It holds vacuum but the solenoid does nothing when power is applied, so it appears that it is stuck closed. The canister vent valve tested good. My hoses are also pretty crusty looking but it doesn't look like they are actually leaking. No codes but it won't clear the evap drive cycle.
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