Loses spark during running

BSCI05

MEMBER
1983 JEEP CJ7
5.0L
V8
4WD
MANUAL
100,000 MILES

Vehicle shut off today as I drove through an intersection. Lost spark but had fuel. Did some tests and found that the ignition module had corroded terminals. Cleaned and fired vehicle up. Drove for five minutes and it shut off again in traffic. Managed to make it home to look further. Purchased new module but cannot get the vehicle to fire off. I reinstalled the old module to see if it’s something bad with the new one but it won’t fire off with the old either. I’m certain it’s the module but not sure what to do now. Any help would be appreciated.

3 Replies

CJ MEDEVAC

MECHANIC
11,004 POSTS

Can you have both modules tested at the parts store? I have gotten New bad modules before, anymore I have them test the new one before I leave the store. (Picture 1)

Key on, what is the voltage at the positive side of the coil?

Do you have the correct coil? (Picture 2)

Before it shuts off, what are the dying symptoms?

Is this vehicle stock or have things under the hood been modified?

Your turn,

The Medic

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Saturday, April 20th, 2019 AT 5:27 PM

BSCI05

MEMBER
2 POSTS

I will get the modules checked this week. The coil was replaced today. The yellow coil is new and the black coil was the existing one.

It’s an 1983 but has an earlier model 304 in it. Original motor was the 4.2 L. Swap was done by previous owner.

I plan to check the items that you mentioned tomorrow.

Thanks for your help.

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Saturday, April 20th, 2019 AT 7:36 PM

CJ MEDEVAC

MECHANIC
11,004 POSTS

For sure let me know the voltage at the positive side of the coil with the key "on".

When it shuts off does it start right back up? Or do you have to drag him back home?

Earlier 304, is it a Prestolite ('78 and before) or Motorcraft ignition system?

If it's Prestolite, we may discuss some of it's downfalls. I switched my '77 CJ-5s 258 Prestolite to Motorcraft as too many things went wrong with the ole Presto parts.

Any noticing of hitting bumps, left or right turns, accelerating, decelerating, etc, when he quits running?

This works at times, while he's idling, shake/move wires or harnesses around "normally" recreating "Gs" in a turn or up and down bumps in the road. See if he cut's off or even skips a little. Wiggle the wires to everything.

Violent and over the top flopping the wires about may move the problem out of the way for now, but then it might reappear in the future, just when you don't need it to! It's best to find it now if you can, so be gentle with the shaking and wiggling process.

The Medic

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Saturday, April 20th, 2019 AT 8:04 PM