I have a 1991 Dakota with a 3.9L automatic. There is something weird going on. When I check for spark at the coil I am geeting a bright strong spark. But at the plugs I get nothing. I already replaced the cap and rotor. What else would cause the spark to not reach the plugs. Before this happened, my battery would always die, and I thought it was my alternator but that was fine and I had auto zone tell me its my voltage regulator and that it is part of the computer. Would a faulty computer be causing all of this? Thanks for any advice.

 

A faulty computer could cause it, yes, but I'd start by testing and/or replacing the crankshaft position sensor... much cheaper place to start.

 

Is ther a certain procedure for testing the crank sensor? Also is there something that would interrupt the spark at the distributor? I just dont understand why it would fire at the coil but not past the distributor.

 

Bad wire maybe?

Here is how the computer works... the coil is always recieving power from the ASD relay. The computer holds the ground for the coil so it does not pass through the distributor. This keeps the coil powered while the distributor is not making any contact so it can do its job. When the crankshaft position sensor reads off the flexplate or flywheel, the computer ungrounds the coil, which is then grounded through whatever sparkplug is making ground. With that said, if there is a bad connection anywhere the distributor system, or a bad crankshaft position sensor, it will not work properly.

For a testing procedure, check the FSM available for download in faq2.

 

here's one from an old guy. the fact you get spark from a coil does not matter. it's all about the color. your going to have to find the colors from the net because i don't remember, but the color of the spark has a direct relationship to the amount of voltage. you may have a blue spark at the coil but a different color at the plugs. if your not getting any spark at the plugs on a 91 your timing is way off. try rotating the dist. back and forth until you get spark at the plugs.
that's the way we did it in the olden times crazy.