84 GMC C2500 Dies After It Warms Up

[Totty101]

Hello-
Long story short I needed to replace the fuel tank. While doing it I replaced the fuel pump, sending unit, bypassed the fuel selector valve and replaced the fuel filter. Ever since then when the truck warms up it bogs down like its not getting fuel and will eventually die. Let it completely cool and it'll fire right up. Ran fine the whole winter I replaced it but when spring came around I started to have this problem. Was stranded one day and a pass bier stopped to help. He thought it was the ignition control module so we replaced that. Did not fix the problem and now it's at it's worst. Hasn't been driven other than around the block in the last year because that's about as far as it gets before it dies. I ran Seafoam in the intake and through the tank and though it didn't fix my problem, it did help it to run smoother. Thought it might be vapor locking so I ran a high temp insulation on the line from the pump to the carb. Still no luck. It is a mutt truck (piece together) but you can't tell by looking at it. Done a lot of little things to it. Any ideas on why my truck does this?

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[Big Chip]

I had a similar problem and when it would start to stumble I could switch the tank and it would run fine for a little bit. I tracked mine down to vapor lock though. I wish you luck!

 

[Totty101]

Where at on yours was it causing the vapor lock? How'd you fix it?

 

[Big Chip]

I have an electric pump that was under the hood and and some funky plumbing. I put a new pump back on the frame rail near the tank and got rid of all the rubber hoses under the hood that I could. I also moved my inline fuel filter so avoid some heat exposure.

 

[Totty101]

Aw ok. I have a mechanical pump. Where was your fuel filter placement originally?

 

[Big Chip]

It was almost right on top of the right valve cover if I remember correctly. I had a problem with my Chevelle vapor locking and not starting so I bought an edelbrock filter setup and it worked to eliminate it.

https://www.summitracing.com/parts/edl-8131/

https://www.summitracing.com/parts/edl-81233/

 

[Charlie]

 

[Totty101]

Thanks for the info. Sorry for all the questions but I don’t want to buy anything until I know for sure that’s the problem. How can I diagnose that’s the problem? Does vapor locking tend to get worse over time? The issue got worse very quickly to the amount it gets driven.

 

[Big Chip]

Mine only did it when it was really hot out on the truck and after the engine was warm on the Chevelle. Is it possible you've got some old rubber hose collapsing when it warms up? Too close to a heat source? I'm not even sure that's a thing but worth checking out.

 

[Totty101]

Lame so youre not sure on how to test for it? I didn't see any collapsing hoses just now. Barely warms up before it will start sputtering.

 

[Totty101]

It is 70 degrees out today so i'm sure that plays a part in it.

 

[1987 GMC Jimmy]

Break the fuel system in half. Feed the pump out of a fuel can and see if the issue repeats itself. Vapor lock is a hard sell at 70*. What’s your carburetor situation?

 

[climb-101]

what are you running for a distributed. i have had some that the modual in the the distributer would get hot after running for a while and kill the truck. let it cool and it would fire right up. drive it till it dies and see if you have spark. that should tell you if it’s a fuel or spark issue

 

[Big Chip]

Lame so youre not sure on how to test for it? I didn't see any collapsing hoses just now. Barely warms up before it will start sputtering.

Lame?

 

[LoStep]

I had a problem like that and it ended up being the wire to the control module in the distributor if it has a vaccum advance the wire will break inside and when it gets hot will expand and contract when cold. also to make sure if its a fuel problem run a pressure gage on your fuel line and see if you lose pressure.