Ok, I'll try to be brief. But I know the more info I give the better my chances of getting the right answer. I have a 94 Dakota sport 2wd 2 door. Originally a 3.9 auto. About 10 years ago I transplanted a 5.2 auto. I drove it for 2 years and the trans blew. It's been sitting since then. Last week I decided to pull the tarp off and bring her back to life. Put in a good used trans, and now I'm trying to get it started. Problem is, it only has spark to no.4. I've replaced the cap, rotor, and pickup coil .With no change...

 

Does the rotor spin while cranking the motor? And how do you know it only has spark to #4 cylinder? Next test is, is spark coming OUT of the distributor cap? If it's coming out on the other cylinders, but not making it to the plug, it's a safe bet your wires also failed.

RwP

 

Rotor turns. Tested spark at all plugs. Then used the known good wire and put it on all other plugs. With no spark at any if them except no4

 

No spark out of the cap? Bad cap or rotor, dude. What else could it be?

Unless it's not on right, and gapping too badly save at #4.

RwP

 

do you have the coil wire on the #4 cylinder tower on the cap? only other thing it could be other than what Ralph said.

 

??? There are multiple things besides what have been mentioned that can cause the problem. Crank sensor, PCM, poor grounds. I'm hoping someone has had this problem and can narrow it down

 

If it's firing AT ALL, it's got crank signal. If it's firing AT ALL, the PCM is firing.

I mean, if it dependably fires on #4 ONLY, it knows when #4 is up to fire, that proves most all of it.

And what ground would kill all but one plug?

I say it again - if the coil is firing each time, and it's not coming out of the distributor but on one wire, it's cap or rotor. That's ALL that's there to pick which cylinder it's firing at any given fire event.

RwP

 

I've seen crank sensors short out, and randomly fire. I've seen corroded computers do all kinds of crazy things. And a bad ground can cause more problems than I'd care to list. And as stated. The cap, rotor, and pickup coil are all new

 

Test for spark AT the coil. See what ya get.

 

The coil is hitting hard