Vapor Lock!

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solli5pack

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Might be worth doing a purge and seal test on the EVAP system with a scanner just to make sure it's working properly. One possible cause that can be checked off the list if it is.
 
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Hodgeee

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Thanks. Not trying to be argumentative, but im not ruling it out. To say it is impossable is 100% incorrect. It does happen to some fuel injected vehicles. It is more common on certain vehicles. If you research it there is a ton of info out there on it, and on tahoes and yukons and suburbans too. Perfect example is on earlier 4.0 jeep wranglers. Now i used to be a mechanic, and only have seen it personally on older carbed models myself.

Not saying, thats whats wrong here, but the symptoms do point to this. The clogged tank vapor system causes difficultiy fueling and pressure build up, and lastly can cause poor running if the vapor fumes from.the tank dont get returmed into the vehicle intake to burn, causing poor fuel mileage. It would not cause these symptoms. So far internet research has been showing it happens more to non return line fuel injection. Theres not a comstant flow of gas in the rails, just direct pressure.

Ive given up on mine. Mine runs great, and when it does happen, its minor. I cant figure it out. Just trying to help my neighbor cause his almost stalls and then surges massively. Mine did this way more earlier but was a non programmed throttle body and it did it all the time. It is so odd it only happens in hot weather, and only when the vehicle engine has been sitting for a little while after it has been warmed up, but niether does it in cold weather. Hes ready to get rid of his, but he said he cant afford another vehicle.
 
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Hodgeee

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Looked through his reciepts from last dealer visit. It shows fuel tank evap system tested ok. Stated common vapor lock symptoms.

TTHAT IS CRAZY. They said that was what was wrong with mine also, and it turned out it was my throttle body.

It sucks when the specific GM mechanic cant figure it out. And they charged him $189 for it. They didnt charge me when they came to the same conclusion, and were wrong. Its a shame. His is older and more mileage than mine but way cleaner and better shape, its spotless.
 
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Hodgeee

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Sorry to respond late. Tested his fuel pressure, its holding pressure to 0 lb loss after 10 minutes. We removed the vapor canister, it was replaced at some point earlier. Put compresser air into the vapor lines that go into the tank, and it blows back out to the vapor canister line freely after i engaged the solenoid, so i dont think the lines are clogged. Didnt remove tank, just sagged it down enough to get to the lines.

Well im giving up on his, not my vehicle. Nice guy, but a lot of work from me, for a guy i see only in passing.

Was hoping someone else here might have had insight. I found on a Silverado/Sierra forum, a handfull of people including two Suburban owners have the same problem, but no solutions either.
 

petethepug

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What’s the history on the fuel pump. If the vapor canister was replaced, likely because there was good reason, did they drop the tank to remove potential pellets? At this point, if there’s no f/p history or there’s a history of installing a knock off f/p, replacing the f/p w/ an OEM unit is the next step. The fuel tank would be scoured for pellets at the same time.

It’s just the nature of the beast unfortunately. Predictable, but still a pita.
 

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