Persistent fuel pressure problem

[peter]

I have been trying to solve this for 2 weeks. When cold 7 psi- runs great. Within 15 minutes pressure drops to 3 psi and within 30 minutes it drops to 0, and the car dies. If I let it sit for 20-30 minutes pressure come back up and it runs fine and then it cycles back to 0.
So far I have replaced the electric fuel pump and main fuel filter, and removed an extra filter at the carb. I do not hear a rush of air when I open the tank fill, so I dont think its vaccuum in the tank. I am wondering if the tank intake has a screen and its getting blocked in the tank? Other ideas to look into? thanks peter

[Naumoff]

It does sound like a venting issue. There is no screen. I would make sure the vent is clear. And if that does not work I would pull the gas tank and clean it out.

[Brent]

Sounds like a vacuume issue in the tank.
Pop the gas cap loose and see what happens.
If your fuel pump is above the fuel level it takes VERY little vacuume to cause a pressure issue.

[peter]

I checked the vent with compressed air and can hear the air coming up through the tank -- it's clear. I also opened the gas cap and there is no vaccuum pressure so I dont think its a vent issue.

The pump inlet is about 6" above the tank outlet and I wondering if the fuel line from the tank up to the pump is the problem. I figure it might be the hose under vacuum is collapsing. It appears to be a braided covered rubber hose and it has worked for the past 4 years.At this point it is predictable, I get about 1/2 hour of run time until the car stops running -- I let it sit 1/2 and get another 1/2 hour... The only other possibility is to drain the tank and check in there for something blocking. Given the predictable timing I am thinking its the hose. Sorry for rambling.... looking for other ideas. thanks peter

[Naumoff]

Rambling is good and asking for advice can lead you to thinking about different things that can cause the problem. Replace the hose and see if it does the trick. Let us know if it helps.

[Brent]

Draining the tank is easy enough to do . Strain the fuel as you drain it so you will know if you found anything. You would have to have some serious issues to collapse a braided hose unless it is that "fake" braided crap that just slips over a regular rubber hose.

[peter]

When I installed the new electric fuel pump, which an exact replacement for the one I have been using (Holley Red) the directions that came with it said it should be installed so the pump intake is not higher than the output from the tank.

My current set up the pump intake is about 6" above the tank output. Maybe this is the problem and I have been lucky for the past 4 years?

[Brent]

The red and blue pumps are push pumps and to operate to their potential they need to push fuel not pull it, however, they will work as a puller. I have seen pumps mounted on the inner fender 12' in front of the tank. Not ideal but it will work.

You can change it but I think something else is the culprit.

4 years of running great is a clue something has happened.

Good luck!

[scott h]

i have a boat that would run out of gas, after much searching i discovered a piece of electrical tape was caught in the pick up tube and would flapper against a screen at the top of the tube. it took me two years to discover it, having been talked out of disassembling the gas tank fittings by more than one "expert". My point? Don't rule out anything! without checking. You seem to be on the right track.