ECU trouble 98 Dodge diesel

woodsrat · Mar 16, 2014

98 Dodge 24v Cummins, I have been having my low fuel pressure warning light come on intermittently. When cold I can start and run the truck as long and hard as I want on the freeway and no problems. After stopping or getting off the freeway the low pressure light starts coming on and won't go away until everything gets cooled off. I have checked voltage to the lift pump and at times there is nothing coming from the ecu to run the pump. I guess I am pretty sure I need to replace the ECU but am just wondering if there is anything else that could be causing my problem, harness maybe? As a temporary fix I have direct battery hooked to the pump with a switch and it has been working perfectly. Also I have seen ECUs priced from $200 to $1000, any suggestions on a replacement.

Lucky Jeff · Mar 16, 2014

Should be able to find one for 200 no problem. 01-02 ECM's are less prone to problems. You can have it reprogrammed to work with your 98.

JOOP · Mar 16, 2014

Have you checked to see what the fuel pressure is at the fuel filter when it gets warm? Maybe the lift pump gets tired when hot. Might need a new lift pump?

Lucky Jeff · Mar 17, 2014

JOOP said:
Have you checked to see what the fuel pressure is at the fuel filter when it gets warm? Maybe the lift pump gets tired when hot. Might need a new lift pump?

He said he had no power to the pump...

woodsrat · Mar 17, 2014

JOOP said:
Have you checked to see what the fuel pressure is at the fuel filter when it gets warm? Maybe the lift pump gets tired when hot. Might need a new lift pump?

No I haven't checked pressure, just have the light that comes on at 5psi. I thought the same thing at first and even bought a new pump, but since I direct wired the pump it has been flawless. When the low pressure light is on there is no voltage to the pump.

Do the 01/02 ECMs have the same plug harness? Where's a good place to get one?

Lucky Jeff · Mar 17, 2014

I asked a friend before, been a few months so I've forgotten. I'll have to ask him again.. He use to keep many on hand. But once the programmers came out, he had no real need for them. I have a fuel pressure gauge that taps into the filter housing as well. Just to give you an idea on how the pump is doing.

Avanteone · Mar 19, 2014

We've had the same issue on these trucks, mostly after pump failures. For customers who didn't want to replace the ECU, simply found a 12v circuit powered ON while running, used that to trigger a relay to run the pump, and left it at that.

woodsrat · Mar 20, 2014

Avanteone said:
We've had the same issue on these trucks, mostly after pump failures. For customers who didn't want to replace the ECU, simply found a 12v circuit powered ON while running, used that to trigger a relay to run the pump, and left it at that.

Well I did lose my vp44 about 10k miles ago. Wonder what makes them start being forgetful? The switch is kind of a pain in the ass but at least it works. Seems to run a little better too, pulls the enclosed sled trailer a little further up hill before having to down shift. Maybe I'll just leave it be for now.