My 96 started to exhibit this dreaded issue at the end of 2020. After reading through the many similar posts, I stated troubleshooting and here is what I found:
The truck stalls and sets code P0320. It won't start again unless I let it sit for several minutes. No spark. After a short period, it starts and runs fine until the next stalling event.
Reading through a bunch of 10-year-old posts, I changed out the ICM, Distributor and Crank Position Sensor ( yes, my 96 has this sensor mounted externally behind the balancer). Still had the same issue.
Then I started going deep. I used an LED test probe to test the PIP and checked voltages on the coil. Everything checked out. Plugs, wires, cap and rotor, all new. I even found a post about replacing the PCM power relay and swapped this with the horn relay. Same problem.
Recently, I noticed while the truck is sitting and will not start, if I leave the key in RUN, the PCM will reset all by itself. I hear the relay click, the fuel pump prime (1-2 sec) and then it will start. I started looking for loose or shorted wiring and could not find anything serious until I pulled the PCM relay diode. This little bugger tested good with the diode check mode on my DVM but it appears the contacts were oxidized and not making good connection. Just by pulling and reinserting the diode, I was able to scratch the contacts clean enough where the symptom appeared to diminish.
The strange thing about this, every time I turned the key on, I would hear the fuel pump prime, indicating the PCM powered up ok. But I am suspecting that when cranking the starter, the voltage dropped too low through the diode (and or contacts) and the PCM relay was opening up.
We just had 7 inches of snow and I ran the truck all morning plowing snow. Ran just fine but I am skeptical that the diode contacts were the only problem. I am now positioned with several signal and voltage probes temporarily wired into the cab to try and catch what the truck is losing when it stalls but of course the truck now starts and runs without issue, at least for the time being but I'm watching and waiting.
1996 Eddie Bauer, 5.8L 110k miles.
Meyer 7' Lot Pro
The truck stalls and sets code P0320. It won't start again unless I let it sit for several minutes. No spark. After a short period, it starts and runs fine until the next stalling event.
Reading through a bunch of 10-year-old posts, I changed out the ICM, Distributor and Crank Position Sensor ( yes, my 96 has this sensor mounted externally behind the balancer). Still had the same issue.
Then I started going deep. I used an LED test probe to test the PIP and checked voltages on the coil. Everything checked out. Plugs, wires, cap and rotor, all new. I even found a post about replacing the PCM power relay and swapped this with the horn relay. Same problem.
Recently, I noticed while the truck is sitting and will not start, if I leave the key in RUN, the PCM will reset all by itself. I hear the relay click, the fuel pump prime (1-2 sec) and then it will start. I started looking for loose or shorted wiring and could not find anything serious until I pulled the PCM relay diode. This little bugger tested good with the diode check mode on my DVM but it appears the contacts were oxidized and not making good connection. Just by pulling and reinserting the diode, I was able to scratch the contacts clean enough where the symptom appeared to diminish.
The strange thing about this, every time I turned the key on, I would hear the fuel pump prime, indicating the PCM powered up ok. But I am suspecting that when cranking the starter, the voltage dropped too low through the diode (and or contacts) and the PCM relay was opening up.
We just had 7 inches of snow and I ran the truck all morning plowing snow. Ran just fine but I am skeptical that the diode contacts were the only problem. I am now positioned with several signal and voltage probes temporarily wired into the cab to try and catch what the truck is losing when it stalls but of course the truck now starts and runs without issue, at least for the time being but I'm watching and waiting.
1996 Eddie Bauer, 5.8L 110k miles.
Meyer 7' Lot Pro