1998 Dodge Ram No spark

Hi, thanks for the donation. Did you check for primary voltage at the coil, engine cranking, dark green wire with orange tracer. If that wire is hot and there is a ground pulse, maybe a bad coil or coil wire. How long since a tune-up?

If no voltage, a possibility is the computer doesn't see the proper cam and crank signals. Without those signals the computer may not ground the asd relay. The asd relay supplies primary voltage to the coil--injectors-- and whatever.

To get to the right circuit, you need to check for fuel too. One easy way to do this is to measure the voltage on the two small terminals bolted to the back of the alternator. One of them must have full battery voltage, but only for one to two seconds after the ignition switch is turned on, then it will go away. What's important is if that voltage comes back during cranking. If it does, you do indeed have an spark problem. Much more commonly though, I'll bet there's no voltage at the alternator. That means there will also be no voltage to the fuel pump and the ignition coil.

All of these things are powered by the Automatic Shutdown (ASD) relay. The engine computer turns the ASD relay on when it sees engine rotation, (cranking or running). It knows the engine is rotating by the pulses from the crankshaft position sensor. That's the guy you gotta check. I can't remember if it lives in the transmission bell housing next to the engine block or if it's in a distributor.

Caradiodoc