Stock C10 tank w/ efi

[carnut$]

I installed a '94 LT1 EFI 350 into my '71 shortbed. I'm using the stock behind the seat fuel tank w/eec. I'm running and external FI pump. I've plumbed the pressure side from the stock (single line) sending unit, and the low pressure return through the passenger side/top tank tube. I'm wondering if my vented gas cap is "breathing" enough. Sometimes the truck will rpm surge & sometimes even die, making me wonder if it's vapor locking.

[ga-stepside]

I have a LT1 in my 280z. How much pressure are you getting at the engine? It should be 40-43 psi. Plus is the pump close to the tank. electric pumps don't pull well, they are designed to push. How big is your input line to the engine? It should be 3/8 with the return no smaller than 5/16.

[carnut$]

I mounted the pump down on the frame rail (under the dvrs door). Gauge at the fuel rail reads 42 lbs.
Pressure side into engine is 3/8" & fuel return is 5/16".
The surging is very sporadic, as well as the dying. Most of the time it runs perfect.

[Andy4639]

Originally Posted by carnut$

I mounted the pump down on the frame rail (under the dvrs door). Gauge at the fuel rail reads 42 lbs.
Pressure side into engine is 3/8" & fuel return is 5/16".
The surging is very sporadic, as well as the dying. Most of the time it runs perfect.

At the time it does this is the tank near empty? Could be loosing fuel pressure from the tank side if in a curve are very low on gas.

[Warrens69GMC]

When it surges can you remove the gas cap while running and it "fixes" the problem?

[carnut$]

It does it so infrequently, it's hard to pin it down. Yesterday it did it parked/running perfectly still in the driveway. I wished I'd thought quick enough to remove the gas cap then to see if it recovers.

[anew4961]

I went through all this on a rear mounted tank. the fuel pump needs to be as close to the tank as you can get it the tank does need to be vented outside of the cab and have a good return line. you can get sending units with two lines