Another question..:does the coil itself have to be grounded?

 

it is the positive terminal that i was taking the power away from. the coil itself should not need to be grounded but the negative terminal does need to be grounded.

 

Ok I guess ill try a few things in the mornin... I'm guessing the control module does all of the breaking connection internally right? Im seriously thinkin I may have a bad module but idk. Thanks

 

Sorry I had to leave last night but your problem lost out to the wife's problem. When momma aint happy aint nobody happy. LOL

The coil body does not have to be grounded.

I was just rereading the thread and I found something I missed. The resistance in the coil you said was 8.18 ohms and I read that as 8.18 K ohms which would have been in spec. If you actually had 8.18 ohms the coil is out of spec. This reading needs to be in the thousands. Sorry I didn't catch that but some times when the mind knows what it should see, the mind sees what it should be instead of what it is. Maybe I'm getting old.

 

We need to look at what happens in the truck not on a test stand. The only true tests of a coil are the ohms test of the primary and secondary windings or an oscilloscope. In a bench test a weak coil will spark weakly but it will spark.

In the truck the power to the coil comes from the battery to the ASD where it stops because the contacts are open. The power to this point is constant regardless of the ignition key position. When you turn the ignition switch to run or start, power is applied to the coil in the ASD relay and the computer. If certain conditions are met the computer grounds the magnetic coil inside the ASD and closes the main contacts inside the ASD. Now the direct battery voltage flows from the battery to the positive side of the ignition coil, fuel pump, injectors, O2 sensor and terminal #8 on the computer. This is physically what happens. So we now know that there is nothing on this truck to make and break the 12 volts to the coil positive to make it fire.

What makes the coil fire is the computer ungrounding the negative side of the coil when the hall effect switch tells the computer to do so. The reason the computer is in the grounding circuit is to control the advance/retardation of the spark to deal with varying engine loads. The alternate grounding/ungrounding of this negative side of the coil is what fires the coil and also what makes a tach work and that is why a tach is connected to the negative side of the coil.

 

If you are not sure about a coil you are looking at as a replacement. Here are the actual specs for the coils that were used on your year truck and some specific replacements. This is not a complete list but should act as a guide.

Primary: 1.34-1.55 ohms

Secondary; 8.0K-12.0K ohms
Chrysler/Essex; 9.0K-12.2K ohm
Chrysler/UTC; 9.0K-12.2K ohms
Chrysler/Prestolite; 9.4K-11.7K ohms
Diamond; 15.0K-19.0K ohms

 

K I had to double check my ohms after seein ur last post and I am gettin 8 k ohms..I traced the pos. wire of the coil it comes out of the computer and then it spices to the relay, injectors, coil, and fuel pump.

 

All of those things are directly connected like I said but the power comes out of the relay to everything else. If you are not getting battery voltage at the coil + you must trace out why. This is usually dirty contacts in the relay.

Remove the existing wires from the coil. Put one of the old plug wires into the center cavity and a spark plug in the other end. Ground the body of the plug. Put 12 volts straight to the positive side of the coil and attach a jumper wire to the negative side. When you ground the negative jumper the coil should charge, and when you unground the jumper the coil should discharge thru the plug with a nice spark. Run all grounds back to the battery negative in this test to eliminate any possible bad grounds. This will test the coil all by itself. If you still have no spark the coil is the problem.

 

I was talking to a friend of mine and told him your problem. He said that he once saw a cracked coil insulator post that tested fine but when fired it shorted out instead of putting the spark into the coil wire. He said you could not see the crack at all. He said that if you put baby powder on the insulator and wiped it all off with a towel the powder left in the crack shows up as a nice well defined line. I guess it is like a poor mans magna flux. Might be worth a try.

 

Ok I did the coil test straight to the battery and I do get spark. Tried it on two different coils....I even hooked up an inline spark tester and it lite up. Now the arc wasn't all that but it was still an arc....so I'm thinkin their both good. One coil was gettin warm during the test and the other not.