Hi everyone, new to the forum but have been lurking around quite a bit the past few days trying to figure this out. Thanks in advance for any suggestions.

So my buddy and I have been trying to get this 91 (built 10/90) Dakota he has running. It's a 3.9 (with HEADERS! Lol) auto 2wd. Fixed tons of wiring, including the famous splice, and got it to throw power to the coil and squirt fuel when it cranks but we still have no spark. Have replaced the hall effect in the distributor. From what I understand, this is exactly the symptom of a bad crank sensor. Now I know there is much debate about whether or not the pre-magnum engines even have a crank sensor, but all the parts stores show the part for this year and I have found stories online about people having found and replaced it. Alas, no pictures. Any thoughts or advice are appreciated, we're dying to get her running.

 

The later crank position sensor is located in the rear passenger side where trans bell housing meets the block, I don't know about earlier ones but if you have one I would guess that it's there. Do you have a FSM?

You should put the vehicle in diagnostic mode and get the codes, that will help you solve this problem. Once you get those you'll be able to hunt down the culprit. A failed CPS will show up in the codes.

Steve

 

Thanks Steve, forgive my ignorance but what's FSM? We don't have an OBD1 scanner; is there any way to pull codes without one?

 

Sorry, FSM=full service manual, or some type of manual that deals with engine electric and fuel management etc. I have a crappy Haynes for B series vans but because it covers the 3.9 and the OD trans it covers most anything that will occur on the Dakota too. It won't have the correct wiring diagrams though.

You can obtain the diagnostic codes by turning the ignition on then off three times, the final (third time) leave the swtich on. The CEL will go out and then watch because it will blink the trouble codes at you, but only two digit codes. You can find the list of codes online. Code 12 is battery disconnected (at some point) to the PCM. Code 55 means end of codes. Watch and write them down, long pause is beginning of another code. There's also a Youtube vid of someone doing it on a mid-90's Dakota.

This is how I figured out that my problem was the CPS, I got a code 11 that said there was no reference for ignition spark.

Steve

 

Unfortunately we don't even have a Haynes manual at the moment. Budget is approximately non-existent as I am currently unemployed. It's on the list for sure though. Thanks, I will pull the codes shortly and see what comes up.

 

Well, I can hardly believe this but all I'm getting is 12 and 55! Maybe a new coil is in order. I tested both of the ones we have (MSD blaster II and a cheap oe replacement) and I thought they were both good. Perhaps I did it wrong though. Will it be able to throw codes if it hasn't run since the battery was installed? I have to steal the battery out of my truck every time I work on it so maybe the computer can't determine what's wrong? I miss carburetors.

 

Hmmm, yeah that suggests there's no problem really, just that the battery has been disconnected. I would test coils again and see, that might be your problem. Borrow a known good working coil and see what you get.

Steve

 

Exactly what I was thinking. How much difference is there between all these old canister type coils? I have one on my '71 International that I know is good. Wondering if I could stick that in the Dakota.

 

Well, the MSD tests almost perfectly in line with the factory specs so I have to assume it's good and still nothing. Could it be the PCM? As I understand it a bad PCM usually won't even show the CEL when you cycle the key.

 

Well I just found out that the PCM we were running before switching back to the old one was a Magnum PCM. So now I have to wonder what damage we may have done to the wiring and such by having the wrong computer in it.