91 Dodge B350 ignition problems

[aluminumfalcon]

This has been an ongoing problem for quite some time and now I'm at a dead end. Im not getting a spark from my coil.
What I did was test the ecm, replace that, replace the coil and all plugs and wires as well as distributor cap and rotor. Every time I put a new part in she would start right up with a nice healthy spark and maybe an hour later just die. Sometimes when testing leads it will start up for a moment.

Is there some cut-off relay or maybe sensor that could be stopping the coil from putting out? It reads 12v but its not pushing.

Any help would be great. thanks

[alloro]

You could have a bad pickup coil in the distributor. If the pickup coil has an intermittent open or short, the engine will run fine until the pulses from the pickup coil stop.

Also, if yours has fuel injectors, there is a crankshaft position sensor that when hot can stop working as well. Either of these sensors will stop pulses and prevent the coil from firing.