fuel problem

[sgt1022]

I have a 71 c10 w/350ci edelbrock carb Holley 110 gph blue pump through regulator at 4 psi. With braided-6 line. After I drive for an hour or so in traffic my regulator starts dropping pressure when I'm at idle. The problem has left me stranded twice. I can loosen a fitting and in a couple seconds fuel starts flowing again and truck starts immediately. My fuel lines are a fair distance away from exhaust heat. I do not have a return line.

[MagmaJct]

Funny. I have a 71 C10 w/350 and Carter AFB (Edelbrock.) However I'm running the stock pump set up.

I wonder what kind of suction that pump's pulling. If you have the wrong gas cap, or if the evaporative emission control system has been deleted, with time, as the fuel level is drawn down in the tank, a vacuum can form. (Like trying to drink from a Coke bottle without letting air in!)

You could loosen the gas cap when this happens and see if it helps.

[sgt1022]

I will try it. IT really only happens only after driving in stop and go traffic or during the daytime hours that's why I think heat is playing a factor.
when I'm on the highway it'll run 4 psi all day long without hesitation.
I feel the pump is heating up cause it slowly cuts out in traffic and takes about 30 sec. to kick in after starting during these times.

[sgt1022]

The only thing on the EEC that was deleted is the canister. That was gone when I purchased the truck. All the lines are there and when I replaced the tank I hooked it back up the same way.

[cdowns]

Originally Posted by sgt1022

The only thing on the EEC that was deleted is the canister. That was gone when I purchased the truck. All the lines are there and when I replaced the tank I hooked it back up the same way.

do you hear a pressure rush when you remove the gas cap?? if yes you aint got it hooked up right

[MagmaJct]

Originally Posted by sgt1022

The only thing on the EEC that was deleted is the canister. That was gone when I purchased the truck. All the lines are there and when I replaced the tank I hooked it back up the same way.

Okay, now we're making progress. The line, that used to go to the canister, where is it now? Is it open to atmosphere? Is it plugged?

The original gas cap is a "vacuum/pressure" cap according to textbooks. By that very short description, I can only assume it's essentially a check valve type venting. That is, it allows air in to prevent a vacuum, yet doesn't allow vapors out. (Since vapors would then vent to the atmosphere, no the canister.)

[sgt1022]

No pressure release when removing gas cap.

The line is open to to atmosphere

[rotten67]

Where is the pump located? Needs to be as close to tank as possible. Even better if it's in the tank. It's easier for fuel to vapor lock under vacuum than pressure.

[sgt1022]

Pump is within 12-14of tank