1997 Jeep Wrangler Engine will not start

The 12 volts at the coil for one to two seconds after turning on the ignition switch proves the ASD circuit is working properly. After that, the ASD relay will not turn on again until the engne computer sees engine rotation, (cranking or running). It powers the coil(s), injectors, fuel pump or pump relay, alternator field, and oxygen sensor heaters.

The engine computer knows the engine is rotating by the pulses from the crankshaft position sensor, a common falure item.

Caradiodoc

Let me clarify my earlier reply. Check for 12 volts at the ignition coil for the first second after turning on the ignition switch. If you turn the switch on, then run to the front of the vehicle, there will not be voltage on the coil. It is only there for one second, so you'll need a helper to turn the switch or you'll need to prop the meter or test light so you can see it from inside the vehicle. If you never see voltage there, I would first suspect my probe wasn't making good contact with the terminal. If there still isn't voltage, suspect the ASD relay, which you already switched, or the wiring to the coil. The Engine Computer is next, but I'd be surprised if he was the problem.

If the voltage is there for the first second, it must come back during cranking. If it doesn't, that's the time to head to the crankshaft position sensor. Since that didn't help, the next thing to try is the camshaft position sensor. According to Chrysler, his purpose is for synchronizing fuel injectors, but on Chrysler vehicles, this sensor will result in no spark AND no fuel if it is defective.

The cam sensor is in the distributor. You can test it with an old pointer-type voltmeter. The signal wire voltage should pulse between 0 and 5 volts during cranking. If it doesn't, replace that sucker.

Caradiodoc

Based on some observations in your first post, I'm going to strongly suggest there is nothing shorted. If you have 12 volts feeding the contacts of the ASD relay, a fuse would have blown when the relay turned on or when you bypassed it.

If I found 1.2 volts at the coil, I would first suspect my meter probe wasn't making good contact with the terminal. After scratching it around a little, and I still had 1.2 volts, I would measure on one of the injector connectors. If you find 1.2 volts there too, ... Happy day! Suspect a break in that wire. The splice would be a logical spot to look. Coroded splices are especially likely to cause some items on a circuit to have power while other items are dead.

Caradiodoc

Wonderful. One more veehickel fixed.

How are you doing with yours ibanezjeepguy?

Caradiodoc