My 93 3.9 Dakota will not start. With days of investigating the ignition system, I have come to a point that I can't explain. I tested the control wires to my ignition coil. The green with org. stripe is 12 v to coil. The grey wire is getting a signal pulse. I used a led test to test between the grey and green going to coil and get the led test light to flash when cranking engine. However there is no spark from coil tower to ground when cranking. Three different coils, the last try with new coil. What am I missing?

 

If you're getting 12V, ASD is firing so the ECU sees crank pulses.

If it's pulsing, the ECU is seeing crank pulses.

Both of those tend to eliminate the crank position sensor as a problem.

How are you testing for spark from the coil?

How good is the mounting connection (the "ground" for the secondary)?

Check the primary and secondary coil resistances. Primary should be somewhere around .95 to 1.20 ohms; secondary should be 11.3 to 15.3 KOhms.

RwP

 

The primary and secondary coil resistance are 1.5 and 13.08k.

The core of coil to the alternator case is .4 ohms. So I would say the mounting ground is fine.

I am testing the spark from the oil by placing g a large screw driver from the coil high voltage pin to the alternator bracket leaving a 1/4inch gap. Then having someone crank engine. No matter how small the air gap, no spark.

 

Use a plug wire, and a spare plug to test for spark. Just ground the plug on the block somewhere, and hold it in place. (but, NOT with your hand.....)

 

I will try that. Thanks

 

After much trouble, I finally solved the no spark problem. The coil blue with orange stripe was getting 12v and my LED test light was getting pluses to the coil grey wire. This made no sence at all. I gambled and punched a new Drivetrain Control Module costing $200. Dakota started right up. Evidently the pulses on the grey wire to the coil were too weak or out of sync and would not fire coil.

 

Now that is interesting........ I wonder if a test light with an incandescent bulb would have shown the same thing, I would also love to put it on a scope, and see how it looks......