I have a 1994 Dakota Sport extended cab that originally had the 5.2L then I put in a 99 Durango 5.9L. I have replaced pretty much every sensor on the truck. Idle Air Control, Throttle Positioning Sensor, Cam Sensor, Crankshaft sensor, New plugs wires and coil, Distributor cap and rotor, O2 sensor, new fuel pump, tested fuel injectors etc even down to new oil pressure and temp sensors. Sometimes it'll drive for hours starting and stopping no problems. Other times it'll only go a couple miles then die and won't start. It will crank but have no spark. After it sits a while it'll start so all my testing has to be spur of the moment when it dies. Someone suggested having someone tap the computer while I crank and both times I've done that it's started right up. Has anyone ever heard of this? I'm thinking it's the ECM (computer) but would like thoughts and opinions before I put anymore money into it. Background on the truck... previous owner blew head gasket on the 5.2 I think he got it so hot all the previous sensors were ruined. Could that kind of overheating have compromised the ECM? No obvious vacuum leaks plus cruise control still works. Runs rich and usually dies when I let off the gas and am coasting/idling. But like I said runs good a lot of the time.

 

Sounds like an old style vehicle starter solenoid going bad except for the stalling.

I would get some Lectra Motive electric parts cleaner ($5Autozone) and clean the computer plug and pins, let it dry (catch the overflow with a rag while spraying) then use an acid brush and put a little bit of dielectric grease on the pins before plugging it back in. You can just use a tiny amount from the little grease packet ($1.49 Autozone) for coating the battery terminals.

 

Ok I cleaned the pins and the plug then put dielectric grease in there but it does the same thing. it just cranks and cranks then i'll have someone lightly hit the computer with an open hand and it will start right up. It could run for an a few minutes then die again or go for a few days on and off without having any problems. It's weird. I can't see any of the solder connections in the computer because it's all sealed but i'm thinking there must be a bad connection inside it somewhere. Should I just find another computer?

 

I think I would check the 3 wire splice under the power distribution center on the left front fender. There is info on it in the FAQ1 section.

 

I recall there is one of our industrious Canadian members who talked about taking the PCM apart and using a stainless steel pin or needle heated up like an old school soldering iron and using it to resolder cracked connections in the PCM circuit board. Thing is I don't remember all he said you'll have to search for that post but the whole thing is covered in a rosin to protect it from weather.
If you can manage to eliminate all other sources including that splice under the relay box it might be worth it to try the PCM fix since you'll only have to replace it anyway if it doesn't work. Look for cracks and shorts in the harness leading up the that plug for the PCM they make a real sharp bend just as they go in.