Hoping to get some help with an increasingly frustrating situation with my 96 Ram 5.2L. It started last year with the truck losing power while driving (engine would come down to idle, throttle input would do nothing) then it would come back to life after a few seconds. It progressivley got worse to the point where the truck would stall, but always restart. Everything I read pointed to a crank sensor so I put in a new Mopar unit and no change.

A couple of weeks ago I pulled the truck out of the garage and left it idling in the driveway. When I came out to leave the truck was off and fuel pump would not prime. I thought great, just a fuel pump - was hoping that was my issue all along. Pulled the bed and put in a new Delphi pump, no change. Truck died on the test drive and took about 5-10 minutes to restart but I got it home.

After some more reading and advice from a coworker I replaced the ECM this evening with a reman unit programmed to the VIN. It started fine (as it has been all week, but haven't dared take it anywhere) and idled perfect for 2-3 minutes then stalled. Fired right back up and stalled again after 2-3 minutes. Now it won't fire at all and fuel pump will not prime. I check for power at the relay and fuse and all good. I assume the pump is getting power as the gauge is still showing the proper level. I will test voltage at the pump when I have a helper on hand.

If anyone has any idead on where to go next I'd appreciate it.

 

Have you tried swapping out the fuel pump relay? It could possibly be weak and failing after running the fuel pump for a few minutes. Also, have you scanned the PCM for any pending or stored codes that might be present?

Lastly, is the battery in good shape and fully charged?

 

An easy test to eliminate the fuel pump relay itself or the control side is to jump the load side (pin 30 and 87). This should make the fuel pump run continuously and if the engine starts and runs fine you know where to dig into. *DO NOT* drive around like this as the pump will continue to pump fuel even if the engine stops for any reason.

 

Thanks for the replies guys. I have bench tested the relays according to the Chilton manual I have and they test good. I swapped them between each other a few different ways (Starter/Fuel Pump/ASD) to make sure and still nothing. I jumped pins 30 & 87 and nothing. I would assume that means there's an issue at the pump. I'll have to wait until I have an extra hand to test if there is voltage there with key on. I could also plug in the old pump that wasn't bad and see what that does.

Bettery is old but voltage is good. Truck sits in the garage on a tender and it has 13.6 volts which should be good enough.

Being that its gotten worse since the new ECM I swapped in the old one for fun and still nothing.

I will note that the truck has an aftermarket alarm that the original owner (my neighbor) had installed, but it is funtioning properly. I don't use it, but it disarms properly (according to the blinking red light) and never caused an issue in the past.

I guess the next step is testing for voltage at the pump and the pump itself. I'd be pretty upset if the new Delphi pump was bad and tend to think something else is going on here since it did this with the old pump as well. Not sure if it matters, but obviously this has progressively gotten worse to the point of the pump not even priming now. Was really hoping it was a relay but its never that easy is it?

 

If the engine just drops RPM, but, continues to run at idle, with your foot still on the gas, the crank sensor is not the problem. I would be looking at the throttle position sensor.

 

Thank you for the insight. You know, I thought the same thing when this first started happening and people told me no way. Looks like I need to stop listenting to those people...

That was how the problem started, but unfortunately at this point the truck won't even start. No way the TPS would cause the pump not to prime, correct? Maybe I have two issues going on at this point, a defective Delphi pump and the TPS.

 

Yeah, I think you are correct there, more than one issue. Verify you are getting power back to the pump, take it from there.

 

Also make sure the fuel pump ground is good. Looking at the wiring diagram the pump and the level sensor use different grounds so the fuel gauge working doesn't mean the pump has a good ground. The ground runs all the way from the pump back to near the PDC, there are a few grounds at the inner fender near it.

 

Had a few minutes so took the rear inner wheel well off so I could verfiy the pump is getting power. I decided before I do anything to just give the connector a good push and jiggle the wires a bit and wouldn't you know it, pump primed and truck fired right up. While it was running I shook the wires in every directon I could and nothing, runs perfect. I wonder if the connector was loose? I dont see how that's even possible since it has the red locking tab.

I definitley have another issue so will go ahead and replace the TPS & IAC valves, but a bit stumped on the fuel issue. Going away for a day but when I get back I'll have to mess with it a bit more. Once it was running nothing I did caused any issues and it fires up every time now but I guess it's possible there's a wiring issue at the pump connection? Would be nice if it were in an easier location so I could really give it a good luck. Everything seemed fine when I had the bed off and truck never had an issue priming before.

 

One more thing - For TPS/IAC what are decent brands? I dont' like to cheap out on sensors and things like that. RockAuto is showing a Delphi TPS which should be OK, but for the IAC they only show Standard Motor, Walker, and WVE.

Maybe I'll just replace the TPS for now. I did clean the TB & IAC valve when I got the truck and it idles nice and smooth (when it runs of course). No reason to replace parts just for fun.