Random Stalling Issue - Not CPS or Fuel Pump

[87LC2]

96 Ram 1500 5.2, will cut out randomly when driving. It doesn't miss, it just cuts out and sometimes will come back to life, other times it will stall and not restart for 10 minutes or so. Not fun when you're stuck in an intersection like I was about 20 minutes ago...Was on the phone with AAA and it fired back up and I got her home.

This goes back about a year. Don't drive the truck much but have done some work to it but nothing has fixed the issue. I posted a thread a while back on here and the consensus was crank sensor. Replaced that with an OEM Mopar unit and no change. Last week I took it out of the garage and let it idle in the driveway. By the time I came out the truck was off and would not restart. I did not hear the pump prime (even when jumping the relay) so assumed fuel pump and just finished installing a new Delphi pump this morning. Obviously still have the issue.

What else can I look at here? IAC/TPS, possible ECM replacement? Any help would be appreciated.

What it does is just cut out when driving. The engine comes down to idle speed and throttle input doesn't do anything. Very weird feeling actually. The truck is still running, but foot to the floor does nothing. Most of the time after about 5-10 seconds it will jump back to life and I'm on my way, but lately its been stalling and not restarting for some time.

 

[KoboldTaco]

I would not jump directly to ECM replacement. On the silly side of things, I had a visual of you needing to add more quarters to the pre-installed coin slot in your dash to keep paying for fuel. I suppose that is my overall feeling each time I get in the truck now days.

You have an interesting issue. The fact that it goes to idle with no throttle response is telling, but you also mention it cuts out completely and takes a 10-20 min reset cycle. That to me seems connection / heat related to fuel pump relay or fuel delivery. It would be interesting to note if you hear the fuel pump during those episodes. Then at least you can start to narrow things down from there.

Reference your rev down to idle and lack of throttle response, I’d pull the circuit information and start looking electrically at connections etc. Have you looked at codes? You may not have an active light but stored codes which could help point you a more solid direction.

 

[87LC2]

Thanks for the reply - It does feel like you have to keep feeding quarters to keep it going

The reason I replaced the pump is that after the last time it stalled and wouldn't restart, I did not hear the pump prime when I truned the key. I was actually happy and thought I figured out the issue. It did end up starting the next day but I figured it was just an intermittent pump failure and replaced it anyway - obviously that's not the case.

There are no codes active or stored - first thing I checked.

It's not always heat related. It has done it with the truck only running for a few minutes. Most times I will just lose all throttle response and then it magically comes back, only recently has is started to stall. When this first started it would restart every time. Only recently has it refused to start for some time.

It's a very odd condition. The truck is running but the gas pedal does nothing at all. I've had nearly every problem you can have with a car over the years, but never something like this. I'd think if it was fuel delivery related it would just stall every time? That's what initially let me to spark and replacing the crank sensor, but even that doesn't make sense. It's like the engine is taking a break and either decides to come back and the truck will run fine or it just dies.

Good idea to check curcuits to rule things out, guess I'll start with the fuel pump circuit and go from there. Still open to ideas if anyone's has a similar issue. It's very strange.

 

[Ramagain]

Stalling to me could indicate vapor-lock. My memory is fading on the 1st gen I had but I know I had a return-less system before I added a supercharger. Is it possible that you have a bad Fuel pressure regulator. As for the fuel pump not energizing, do you have an alarm system that's causing electronic glitches?

 

[87LC2]

I just replaced the pump assembly which includes a new FPR. I guess it's possible both are bad, but not likely I'd assume.

You know - There is an old alarm system in the truck but it's never caused my any issue in the past. When I disconnect the battery the truck will flash the hazards and not start until I press the button under the dash, but other than that no issue. I think if it were causing an issue it would be a bit more constant? I have been meaning to remove it, maybe now is a good time.

I read another older thread on here about a similar issue that ended up being a simple PCM repair. May open it up and check solder joints to see if anything looks off. I did start and run the truck yesterday and it was perfect. Never left the driveway, but let it run for 5 minutes or so and not one hiccup, started every time...These are the worst type of problems, would love it if it were just dead and threw a code, haha.

 

[87LC2]

Little update for the week - Checked fuses, relays, and wiring all the way back to the pump and everything was perfect. In fact, the truck primed and started first crank all week whenever I tried it. Figured I would take it out again and of course it left me stranded after 10-15 minutes of driving. Got it started again and its back in the garage.

After reading countless old threads and listenning to a guy at work who has a few of these older trucks I decided to replace the ECM with a reman unit. It came today and truck fired right up and ran great. After about 2-3 minutes it stalled. Fired it up and it ran again for another 2-3 minutes and stalled. Now it won't do anything, pump won't prime at all and is still getting power at the relay and fuse (couldn't check the pump since I'm by myself, but after everything that's going on I really don't think there's a wiring issue and I doubt the new Delphi pump is bad). I guess it's possible the new pump is bad, but that would be very unlikely.

What else could this possibly be? There is as aftermarket alarm that was installed way before I owned the truck. I don't use it and the only time I mess with it is to flip the switch whenever I disconnect the battery. It seems to be working as it always did, but I guess that could be causing some sort of issue? It's wired in under the dash and when activated the truck won't crank. When deactivated the truck will crank, but pump doesn't prime and truck won't run. I assume it's wired into the ignition and not effecting the fuel pump at all. Is that a fair assumption?

Really not sure where to go from here.