Truck left me stranded today.

81 Chevy K20, 4 speed, 350 - electric fuel pump & original carb

We were heading downtown today and, out of the blue, the truck stumbled and lost power. I switched tanks and restarted immediately (both tanks filled yesterday). We get in the parking garage and, of course, it dies again. No restart this time. I was able to push it out of the way after a brand new white Caddy SUV scraped her car across my bumper. I let it sit for about 30 minutes, pulled off the air cleaner and it started up and got me home.

It was hot today, I was running the AC, but traffic wasn't bad and the truck has been significantly hotter.

Could it be vapor lock?

sgrinavi said:

81 Chevy K20, 4 speed, 350 - electric fuel pump & original carb

We were heading downtown today and, out of the blue, the truck stumbled and lost power. I switched tanks and restarted immediately (both tanks filled yesterday). We get in the parking garage and, of course, it dies again. No restart this time. I was able to push it out of the way after a brand new white Caddy SUV scraped her car across my bumper. I let it sit for about 30 minutes, pulled off the air cleaner and it started up and got me home.

It was hot today, I was running the AC, but traffic wasn't bad and the truck has been significantly hotter.

Could it be vapor lock?

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Sure it could be vapor lock, though I don't know your electric fuel pump setup, vapor lock normally occurs before the pump, the reason being is after the pump is under pressure, and just like with your radiator the pressure increase also increases the boiling point of the fuel. But an electric pump that is failing could cause this as well. Also could be an ignition module or coil. Sometimes with the module and the coil they heat up, quit working, cool down and start working again. You'd need to get it to do it again and see if you loose fuel or spark. Though in my mind if your like me and rely on your truck on a daily or regular basis it would be a good idea to replace the module and coil if they are original 40 year old parts, or just unknown age as PM maintenance. ACDelco or Standard motor blue streak seem to be what folks have the best luck with.

And what about the "and the truck has been significantly hotter" you mean coolant temp? If the engine is overheating that certain can cause other problems, and I'd fix that first.

SirRobyn0 said:

And what about the "and the truck has been significantly hotter" you mean coolant temp? If the engine is overheating that certain can cause other problems, and I'd fix that first.

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Yes, the coolant temp. It was about 180 today, it's been as high as 210 when one of my fans crapped out.

In line fuel filter looks suspect too, so I swapped that out.


I will change the coil, cap and module. Can't hurt. THANKS!

sgrinavi said:

Yes, the coolant temp. It was about 180 today, it's been as high as 210 when one of my fans crapped out.

In line fuel filter looks suspect too, so I swapped that out.

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I will change the coil, cap and module. Can't hurt. THANKS!

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Your welcome. Just make sure to use quality parts for the ignition system. If you didn't know where it comes to the cap and rotor there are two types of contacts they make aluminum and brass, the brass contact cap and rotor are better. Yea, that fuel filter doesn't look all that great. Glad to see your using a wix filter, I use them myself.

Don't forget the filter in the inlet of the carb.

My question, why are you running an electric fuel pump on the 350? Engine mounted fuel pumps have been very reliable for many years. Electric fuel pumps do not like heat. That is why all modern electric pumps are mounted in the tank. The fuel in the tank keeps the pump cool.

Dmack said:

Don't forget the filter in the inlet of the carb.

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That was changed about less than 1000 miles ago.

Turbo4whl said:

My question, why are you running an electric fuel pump on the 350? Engine mounted fuel pumps have been very reliable for many years. Electric fuel pumps do not like heat. That is why all modern electric pumps are mounted in the tank. The fuel in the tank keeps the pump cool.

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That's what was on the truck when I got it. Without a safety switch no-less! I've added one since along with a relay.

sgrinavi said:

That's what was on the truck when I got it. Without a safety switch no-less! I've added one since along with a relay.

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Seriously consider going back to the mechanical pump with a return line. The thing is factory electric in tank fuel pumps are very reliable, but frame mounted aftermarket pumps are not. Doesn't seem to matter which brand. Most of the guys I know running electric pumps carry a spare.

After I swapped to EFI, I ran a frame mounted pump for all of a week before it overheated and almost left me stranded on a trail. I ended up swapping both tanks with new EFI tanks and in tank pumps and have been great since

Ft Myers, hurricane, filled both tanks yesterday, water in fuel possibility?
I know it’s been a month, but…
Otherwise, regarding your fuel pump, first, when it wasn’t starting did you hear the pump and was it filling your fuel filter? Or did you not look at the fuel filter to see if it was getting gas?
Also, electric fuel pumps don’t generally work intermittently in my experience. Generally they’re either working or not and they don’t come back to life a few minute later.

LS swap.

Grit dog said:

Ft Myers, hurricane, filled both tanks yesterday, water in fuel possibility?
I know it’s been a month, but…
Otherwise, regarding your fuel pump, first, when it wasn’t starting did you hear the pump and was it filling your fuel filter? Or did you not look at the fuel filter to see if it was getting gas?
Also, electric fuel pumps don’t generally work intermittently in my experience. Generally they’re either working or not and they don’t come back to life a few minute later.

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Water in the tanks is possible, although I've used the same station several time since the storm without issue.

Yes, pump was running, but, no I did not look at the filter. It could easily have been a failed pump.

I'm not sure why it was switched out, I might go back to the mechanical

Regardless of it starting and running fine again, where is the fuel pump mounted?
I have a similar scenario (carb with electric pump) but don’t have a choice with this engine since it has no provisions for a mechanical pump.

Further away from the tank and the higher it needs to pull fuel, the worse it is for an electric pump. I bought the truck with the e pump mounted up in the engine bay.
Yes it was a cheap pump, but I killed 3 of them each in less than 2 or 3 tanks of gas.
Mounted a similar little cheap pump back down by the fuel tank valve (and new fuel lines and clean power with a timed relay like you) and I’m still skeptical but that pump has now lasted for, idk many times longer than the others.
I haven’t figured out a clean protected location to mount a better quality external pump yet. But it’s on the to do list.

Grit dog said:

where is the fuel pump mounted?

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About 6" in front of the switching valve (under the rock guard). About as close as you can get I suppose.