Vapor lock on hot day.

[matt921]

So i have looked through out the site to find a little to no information on how to fix this. I was driving the car the other day and it would just randomly die after about 30 mins of driving in 100 degree heat. Popped the hood checked for spark it popped away with the wire off. Moved on thought my maf might have came off still good. Then looked at my fuel pressure gauge and it was down to around 20. so i cracked open the fitting and it just hissed and then some fuel would spurt stop hiss spurt.

I deal with this at the shop i work at, as we build carbs and it sometimes comes up. So i let it sit for a few mins cracked open the fitting to vent pressure. Tightened it up turned it over and my buddy said it went right back up to 40 psi. then ran great. Drove about ten mins and bam again. Same thing. so i got on here seen some dudes having issues with there fuel caps not venting. So i took mine off yet again 20psi did the same thing cracked it open and it started and ran for about another 10 till i got home. The pump is a oe replacement that has only been there for about 300 miles the fuel filter is about a month old. I did smell alot of vapors up by my canister. I don't know if maybe its not venting back to the tank for if i just got te fuel lines to hot an they started to vapor the fuel. If anyone has had this issue before please lend some ideas.
Thanks
Matt

 

[DavzGN]

Can't vapor lock an efi system with return. Most likely the ignition module is going. Gets hot and quits working.

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[matt921]

so let me get this right. what your saying is there is no way that fuel will get to hot enough on the way to the injectors and the fpr and drop my fuel pressure from 40psi to 20. Then when i open the line it doesn't shoot fuel out of the line just the vapor thats not a vapor lock. Also the module is a 87 module with a 87 coil pack and a caspers harness less then a month old. Also i drove it yesterday in 85 degree weather for 30 mins got up to 185 and the module didn't break up or cause any issue. I've seen 750hp lt1 with 255 pump vapor lock a efi system. vapor lock is fuel getting to hot vaporizing before it gets to the injector or the carb. There are some carb cars that use return lines and still vapor lock. I'm not trying to be a dick man but when i open the fuel line on the pressure side and get vapor coming out instead of fuel........

 

[charlief1]

A "vapor lock" can only occur when the fuel line heats up and the fuel pump can't suck anymore fuel. Since your car has a pusher pump that's in the gas tank, it's impossible to vapor lock it.

 

[matt921]

ok then forget the lock part. But this still doesn't explain why my fuel pressure went down to less then half and no fuel would come out just vapors. Then once I cleared the line it would start . I did go to a different gas station yesterday and I drove it today 95 degrees and I haven't had any issues. Learning that explains why the gta with the lt1 would do that. It had a inline Mallory so that makes a lot of sense.

 

[charlief1]

There are several different possible things that can cause this. Fuel pump not getting power for some reason would be at the top of the list.

 

[matt921]

I do not have a hot wire kit. maybe I should look into this

 

[charlief1]

That would be a good start.

 

[JDSfastGN]

The vent line from the tank to the charcoal canister is blocked not letting the tank vent. You have to replace the fuel with air and when its blocked it will cause a "vapor lock" in the tank. I just went through the same thing.

 

[trixdout]

Have you thought about one of your injectors being stuck open? Check your oil and smell it. Does it smell like fuel?

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