I'm working on an '89 Dakota 3.9L V6 auto that has been sitting in a field for 3-5 years (present owners can't remember). The owners' dogs trapped a critter in the engine compartment and managed to tear out all the spark plug wires and half the hoses getting to it. The engine cranks, but I can't get spark from the coil. It is getting 11.7 V to the coil terminals, and I got 11.7 V when I metered the output. When I cranked the engine, it dropped to 9V. I replaced the coil, but no change.

Any suggestions?

Thanks.

 

Spark is controlled on the OTHER side of the coil from the 12V side.

So - time to check and see if anything's coming from the ECU.

I'd suggest a PDF of the factory service manual for the wiring diagrams to help. As I type this, there aren't any, but the paper ones are under $30, cheap for what you get.

RwP

 

When my '79 CJ7 was frying ECM's as fast as I put them in, a friend back-converted it to points ignition. Is there any way to do that to a Dakota? I seem to negatively affect anything with a computer in it.

 

Also, right now, all I have is a Chilton's manual. The schematic has one side of the coil going to B12 on the ECM, but it isn't marked in the schematic as the positive or negative terminal. Which side should I be checking?

Thanks.

 

The flow normally goes through the Auto Shut Down (ASD) relay, to the + side of the coil, the - side goes to the ECM.

Which side you should be checking depends on what you're checking for *grins* But if you have 12V at the + side, then it should be good to there. So you need to check the - side continuityi to B12 on the ECM. If that's the pin - Chilton's has been known to put completely erroneous wiring diagrams into their books before.

As to converting to points - the 3.9 is an uneven-fire motor with an uneven-fire pattern. As far as I know, you'd have to have a custom cam for the distributor (cam as in "that thing the points rides on", not cam as in "camshaft inside the motor!) to use a point style distributor. So I'd say "No". Could be done, but there never was a vacuum/centrifugal distributor made for the 3.9 since it was always electronic ignition.

Again, before you fight it too much, if you want the info it RatNaw!! try AllDataDIY.COM or http://www.eautorepair.net/Marketing/Default.asp and pick up a 1-year subscription for your truck. Those can be had for a bit less than the paper copy, although I have both AllDataDIY and the paper (and a PDF!) copy.

RwP

 

Well, the Chilton's has all '89 gas engines as having a 60-pin ECM, but the one in the truck has 14 pins, so, yes, I was beginning to lose my faith in the book. I'll look into that online manual.

I guess a good theory for now is that the dogs in question severed the - side wire somewhere between the coil and the ECM. If that proves wrong, is it possible that the hoses they destroyed had a vacuum sensor that provides the input to the ECM to let it know when to fire the coil?

Thanks again for all the help.

 

I don't THINK there's a vacuum sensor for that. It's relying on the signal from the Hall effect or reluctor in the distributor. May want to check on the distributor wiring also.

Yours should have both the 60pin and the 14pin connectors, right?

RwP

 

Well, it helps to actually look at the owner's manual. It's an '87. Where I got '89, I don't know. That explains a few things.

In other news, anybody know how to edit subject lines?

 

Yah, that does make a bit of difference.

The '87 FSM is also on Ebay, BTW.

Same basic stuff - the ECM does the fire, so if it's not getting a crank signal or has some other problem, you won't get spark.

RwP