CSFI system gremlins

[CoppertopT/A]

Having a little head-scratcher with this system. The power plant is a 1997 350, its in a grumman food truck.

When you turn the key ignition to on the pump will prime and will read 60psi on a fuel gauge. The truck starts just fine and idles fine for 2-5mins. However if you start to drive it let it idle longer than 5 mins the fuel pressure will constantly drop until the truck stalls off. You can if you're quick cycle the key off than on (while the truck is running) and the pressure will spike back up to 55psi and continue to run fine.

The regulator and pump have both been replaced and the problem persists. There are no noticeable signs of a leak, on ground/in the intake.

Any help or direction would be greatly appreciated.

Thanks

[DIGGLER]

must be electrical. possibly the fuel pump relay tips making a poor connection. as they heat up the pump dies off.

[MonteC]

Id monitor how many volts are going to the pump.

[ElecTech]

Fuel tank not venting. Open fuel cap and run it to see if the pressure holds. That would be my first test.

[GreebeanZ28]

Sounds like what one of my cars is doing.