Fuel Pressure Problems...
We're having issues with our beast again. Any suggestions will be great as we're about to pull our hair out.
To start, we have a Mobile Traveler on an 84 e350 chassis with 460 engine.
It had a hard start issue so we put a non return valve (back check valve) because we thought the lines might be bleeding back to the tank. We put a fuel pressure gauge on and tried to turn it on but it wouldn't get more than 3 psi.
At this point we changed the fuel pump, new fuel pump won't get more than 3 psi either.
We found a blown fuse (15A module) and replaced it and reset the inertia switch then it got 5.5 psi and started but died in less than 3 minutes.
We dropped the tank, cleaned it and blew out all the lines, put it all back together and got about 3-4 psi but still no start. Tried starting it again and the fuel pressure dropped and now we cant get the gauge to move at all so at 0 psi now.
The fuse was blown again so replaced it again and reset inertia switch again and still at 0. The wires on the back of the fuse block all look good (none burned or exposed)
The relay works, the pump turns on and primes, the inertia switch has been reset, we have a new oil pressure sending unit, and we're running out of ideas.
Our voltage at the pump jumps (from 3-13 and every number in between) so we tried connecting it directly to an external battery, both positive and ground, and still get no fuel pressure.
We have also removed the non return valve in case that was the issue and still nothing.
Any ideas are more than welcomed! HELP!!!