i have a 89 3.9 4x4. i am not getting any high voltage spark out of my ignition coil. ive replaced it about 3 times just in case, ive replaced my distributor just to try and see and still nothing (it came with the controle unit) but switched it back because it still didnt and my old one tested fine. im getting a constant 12v from my fuel pump when ever the engine is turning over and a pulsing 12 +- from the bottom wire going into the ignition coil with both distributor, its got new wires and the fixings. im some times getting 12v out but not the 60000+- im supposed to ive tried by passing the positive, the neg to a ground, both at the same time, iv tried to see if i could get the coil to fire off the truck just on the battery but only got a 1/16 blue spark probably about 12v out of it. iv talked to about every one hew works in auto zone, orilies and every car guy i know. i got a ceramic resister because they said it might be it but im pretty sure they aren't on this year, it doesn't have the cam position senser ether on this year.

any help would be great and fast im getting out of the marine corp soon and need it to be running. thank

dylan

 

The only thing I would suggest is trying replacing the computer? I would also before even doing that reverify the wiring. Make sure nothing is broke or cracked. Also, check you grounds. No, this model does not have a ballast resistor.

 

Did you try pulling codes?

 

iv checked the wires they seem fine, it doesnt give any codes it just wont send spark it there a way to test where you get the full spark. also is it suppost to ground out threw the mounting brackit, and every way iv seen to check the bottom wire it doesnt say if its suppost to have cont. to the block or gust pulse the power.

 

The Factory service manual has a FTS (Failure to start test) diagnostic procedure. I can scan some of it if needed.

You say you had voltage on the positive coil terminal when cranking.

To narrow it down:
1) Have someone crank the engine for 5 seconds, while you put a voltage meter on the positive coil terminal.

A) If voltage on the positive coil terminal stays around 10-12V for the whole time the engine is cranking, then it's the either the computer/SBEC, the coil, or a wiring problem.
B) If voltage on the positive coil terminal drops to zero after 1-2 seconds then it's something between the distributor pickup and the computer.

 

I am in agreement with 90dakotaconvertible. Its going to be the computer. If you have 150,000 or more miles on the truck The parts that make up your computer have a miles restriction them . Ones these parts reach that restriction they will start to fail. So buy a new computer make sure it is pre-programmed before you buy it. Good luck.

 

okay huh milage restrictions? this aint like oil change required for warranty.. parts fail when they fail not cause of milage ..

its older it wont need any special programing and should be fine out of the box. its not like newer computers that are specific to each vehicle due to GMLAN/Canbus/ ect....

Anyway it does sound like the PCMM has gone out if you have the guts you can pop it open and try resoldering all the joints, but at that rate easier to spend 200 on a new pcm..lol

 

so get a new one. there are a couple of junk yards with a bunch of the gen 1 dakotas or should i just go for broke, also im thinking of putting a 318 in shortly before this happend any thought on what computer would be better, would a v8 model work if i swaped the engine or will it not mach up?

 

You will need to get a 318 computer for a 318 engine. Try and stay with pre 1996 so you don`t need to dig around for all the OBDII guts you need. Plus you can actually find the 1990-1995 MOPAR 318 computers for new here and there, the 1996 MOPAR computers might as well be a legend for how hard they are to find

 

This is the first I have ever heard of this. Must be a secret they forgot to cover during my trade school, and almost all my cars must have forgotten too.