No spark

JEREMY L.

MEMBER
1985 JEEP CJ7
4.2L
6 CYL
4WD
MANUAL
185,000 MILES

Did all tests recommended replaced ICM, pick up coil, ignition coil, and ignition switch and starter solenoid and starter motor! Still no spark out of coil. While using a remote starter from under the hood with the ignition off when you let go of remote starter button the vehicle coughs and sputters like it wants to start but I don’t get the same thing when key is on. This being on a fresh rebuilt 4.2 with Weber carburetor. We fired it up to break in the motor. Ran it for 30 minutes in garage then went for a drive and made it two blocks and had to be towed home. No spark. Any thoughts?

5 Replies

94 TRANSAM

MECHANIC
680 POSTS

Hi, thank you for using 2CarPros. Lets see what we can do to get you up and running again.

Attached you will find the wiring diagram for your vehicle. It is a fairly simple system so there aren't many choices for failures. I would start with tracing your 12 volt feed all the way through the system. Where ever you lose it is where your failure is. Please note the neutral safety switch may be in that circuit. The diagram is not clear on that so test the switch for function as well.

Give this a shot and let us know how it turns out good or bad, we'd like to hear back.

Thanks, Rich

PS. The 2 lines that come up out of the module. The left goes to the ignition switch. The right goes to the alternator.

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Monday, August 12th, 2019 AT 8:05 PM

JEREMY L.

MEMBER
7 POSTS

I’m getting 12 V to every all the wires until I plug the positive wire on the coil to the coil and it drops to six point something volts unless I’m cranking it over in which case it climbs which in turn makes the starter solenoid have the same 6.5 V unless I’m cranking it over is this correct

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Wednesday, August 14th, 2019 AT 10:24 AM

94 TRANSAM

MECHANIC
680 POSTS

No it is not. You should maintain 12 volts. Is there a ballast resistor on it?

Rich

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Wednesday, August 14th, 2019 AT 4:31 PM

JEREMY L.

MEMBER
7 POSTS

Sent a remark from another Tech that stated voltage drop was normal? So I’m a little confused.

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Wednesday, August 14th, 2019 AT 4:50 PM

94 TRANSAM

MECHANIC
680 POSTS

I am sorry, I misread your post. First, do you have a radio interference condenser on the positive terminal of the coil? If so disconnect it and try it. The condenser may be shorted sending all the voltage to ground.
I have looked up your ignition system and some no spark diagnostics. They all say the electronic control unit or the coil are bad. I know you say you replaced them but new parts can be faulty. If you have 12 volts on the green wire from the electronic control unit both key on and when cranking then I would say that it good. I would then do an ohms test on the coil and make sure it is a good coil.

Rich