I bought this Dakota about 8 months ago. At that time I did a basic tune up. New plugs, wires, cap, rotor and coil. It developed a sputter that would come and go. A code would come up when not running well and go away after a few miles of running very well. I don't remember the #, but the code read a rich mixture at the o2 sensor. The bad run condition worsened until it wont start at all. The starter turns with no spark. I've thrown parts at it like a fool. New camshaft sensor, new crank shaft sensor, new ASD relay. The fuel pump kicks on when key is turned, for a second. It has fuel pressure at the Schrader valve. I have check all the fuses with a light, they all have . power with the exception of the o2 sensor fuse. I have read many postings on this issue and tried all the suggestions. I have tested power at the coil with key turned on and then during starting. Each wire to the coil would get power for the split second that the fuel pump kicks on, then nothing. I have unplugged the o2 sensors to see If that helped. I've searched for the notorious wire splice #115. Coming from the fuse box towards the firewall the wires look good. It's a 97 with the 3.9 v6. Manual tranny. only 90,000 miles but the undercarriage was corroded and rusted like it had been exposed to salt water but had a clean title. I cleaned all that up and was driving it as a get to work truck when this started to happen. Any ideas would be greatly appreciated. Thanks

 

The PCM should provide power to the coil for a few seconds at the initial key turn, and then, it should re-engage when the PCM sees the engine turning. (and the fuel pump should kick on again as well.) If you aren't getting power to the coil while cranking, check and see if the fuel pump is running while cranking.

Welcome to DF!

 

ASD relay fires the injectors, coil, and fuel pump. PCM has to see the engine turning over for it to activate the ASD relay other than key-up self prime. The PCM looks at the crankshaft position sensor to dictate when to fire the ASD relay/fuel pump/ignition coil, then uses the combination signal of crank and cam to determine when to fire injector #1.

 

Pay a dealer a diagnosis fee, so they can zone in on the issue for you. Fix it yourself, once you know the cause.

 

Thanks to all. How do I check to see it fuel pump is on during cranking and if it is not does that mean that the PCM is bad? Paying for a dealer diagnosis fee sounds like a good idea as well.

 

Have someone else crank the engine, while you listen for it.

 

If it has fuel pressure at the Schrader valve, then there is only 2 options:

1) Fuel pump primes but does not run, injectors do not fire
2) Fuel Pump primes and runs, injectors fire.

I don't have a 97 FSM to reference where the O2 sensor fuse draws from, but it's possible that there are multiple O2 fuses for the CA emissions arrangement, but the 49 state emissions only uses 1 of them.

1) Unplug the ignition coil, and put a test light or voltmeter probe across the 2 pins in the connector. Keep your hands clear of the belt tensioner (or remove belt altogether). Have somebody else spin the motor over. Determine if you are getting a voltage pulse.

2) If you do not get evidence of a voltage pulse, remove the probe from the black wire in the connector, and take it to a good ground (leave the other probe in the coil's red/orange wire). Spin motor over again. If you get voltage, then the ASD relay is activating and supplying voltage to the coil, fuel pump, and fuel injectors.

3) If both of those fail, then place the probes between battery positive and the black wire in the coil connector. Spin motor over again. If you get a pulsed signal, then the PCM is sending the correct firing signal to the coil.

If, after those 3 tests, you are not getting any kind of power signal from the ASD *NOR* a ground pulse from the PCM, then the PCM is not aware that the engine is actually spinning over. Check all 3 connections on the PCM, as well as the crankshaft position sensor (behind passenger cylinder head) and the camshaft position sensor (in the distributor). Both electrical connectors are behind the distributor.