Fuel Pump/Electrical Problem
 

Hello again all,
Sorry to not be posting much but I've been away due to work.
Before I left I had to replace two rusted gas tank straps on Old Red (my 1989 W-140) and while I had the tank out I pressure-washed the entire underside of the truck. I put everything back together but now I have an interesting problem. The truck will start and idle just fine but after about 5 to 10 minutes of driving it acts as if it's running out of gas, even though the tank is full. It will finally stall out, then I'll turn the ignition off, then back on, and it'll run just fine again for another 5 minutes. I can repeat this cycle as long as you like. When I turn the ignition key to on I can hear the electric fuel pump kick in so I know that's working. I was thinking maybe I've got something electrical shorting out but all my connections look like they are ok. I changed the fuel filter but that didn't help at all. It may still be electrical and I'm starting to lean towards a fuel pump going bad but I'm not sure. What do you guys think?

Good Question. The fuel pump is in the tank right?

Hook up a fuel pressure gauge and monitor the fuel pressure

If it is a TBI system there is a procedure of pinching the fuel return line or removing the vaum hose to the fuel regulator, both should raise pressure. I would suggest getting a manual with these procedures and give it a check over.

The pump is in the tank, yes. I hadn't thought of putting a fuel pressure gauge on it though I should have. The odd thing is everything worked fine before I pressure washed the underside and that's what had me thinking it's an electrical issue. On the other hand when I dropped the tank out there's a pretty good possibility that I loosened up 20 years worth of sediment and mabe that is killing the pump. I'll put a fuel pressure gauge on it today and tell you what I find. Thanks!

What I have done for my '95 Ram, is rent the fuel pressure test kit from Autozone. I then plumb-in the gauge, and then set it under my windshield wiper [so I can see it!], and drive around town for a few days to see if fuel pressure is my issue! The spec for mine was 45-55 psi. I saw it drop to 15-20 psi when it started acting up, and affecting, the motor. Good luck troop! BTW, happy belated Vets day Bro!

OK, I'm an idiot. When I went to connect a fuel pressure tester I realized the problem was simply a kinked fuel hose. It was beneath the air cleaner where I didn't notice it but i still feel dumb for not thinking of it sooner.

Ouch...your not cause you came here and asked questions.

That's great. I like the easy ones even if it is something I overlooked. Better than being at it for days. Good job.

I just had the same problem. It was a split rubber hose in the fuel tank.

polaraman