CJ: No Spark, PLEASE HELP :(

[jokers4x4]

Electrical problem
1984 Jeep CJ7 6 cyl Four Wheel Drive Automatic 118000 miles

Driving home the other day stalled at a stop light and wouldn't start. Next day started, drove onto tow truck
. got it home and nothing. Replaced spark plugs, wires, cap and rotor, coil, and starter selenoid, and ignition switch. No spark when trying to crank, but when you turn the key back it sparks once then quits. my jeep is my primary mode of travel. any Ideas are greatly needed and appreciated. lots of time no money.

[lakev2]

Your jeep should have the ford ignition control module on the fenderwell. That module provides votage to the coil make sure you are getting the proper outputs outta the module.

Sorry can't be more specific, i changed all my ignition out and can't remember the nuances of the original setup.

[jokers4x4]

I think mine is mounted on the steering colum. don't know what the proper out puts should be.. If you could let me know... thanks joe

[aw12345]

Since it's a Ford Ignition module, it's not uncommon with those that the ignition switch does not power the ignition module while cranking is generally in the ignition switch. Probably would not hurt to do the nutter bypass either. Do a search for that one have had problems with the computer part of that before, it would kill the ignition. If I have time in the next couple of days I could probably find you a wiring schematic of the ignition system. Would show you where power and grounds are as well as testing methods

[Jerry Bransford]

The coil has a constant +12 volts applied to one side of it when the ignition key is on. It produces a spark when the ignition system provides a ground to the other side of the coil. That ground connection is "pulsed" by the ignition system to provide repeating sparks distributed via the distributor. That it sparks when you turn the key off means the coil is ok.

I would 1) verify the coil is getting +12 volts when the key is on. If it's not, I would suspect the ignition switch, ballast resistor, or resistor wire. They are what provide +12v to the coil. 2) If the coil is getting +12v, then it's time to suspect the ignition system. If yours is old enough to use points, check the points.

[jokers4x4]

getting 7.5 volts at the coil, where is that ballast resistor at. Any other info. thanks

[jokers4x4]

please if you find a good wiring diagram. my email is kerrijoe96@att.net. thanks

[Jerry Bransford]

getting 7.5 volts at the coil, where is that ballast resistor at. Any other info. thanks

That sounds like the voltage you'd get in the 'On' position which is supplied by the ballast resistor or resistor wire. In newer CJs like yours, it uses a resistor wire instead of a ballast resistor. Well, that doesn't matter anyway as it appears that particular resistor output connection is ok.

So when you turn the ignition key to 'Start' does that 7.5 volts jump to 12 volts or does it shut off? If it shuts off, that pretty well means the switch isn't providing the +12v the coil gets during startup to provide a bit hotter spark until the key is released to the 'On' position. The 'On' position provides the coil that lower voltage via the ballast resistor or resistor wire. The Start position provides the coil a full +12 volts.

[6spdYJ]

Have you had your battery checked? If it is weak, it can show 12V until it's under load. Electricity works like a teeter-totter. It will give you all the amps it has, at the expense of voltage. 12V systems have an operating range from 10.4V-14.2V. If the amp draw pulls the voltage below 10.V, it won't start. Also check your alternator, if the diodes are shorted, it will send power all over your electrical system. No telling what enabling or blocking signals it may be sending. Worse yet, it reduces the difference of potential (voltage) between positive and negative of your system. Be sure to check the polarity of your coil.If 12V is applied to the negative terminal, you will only get 1/2 of your coil voltage to the spark plugs. Check connections of both ends of both battery cables, if loose or corroded, they can cause a low voltage/high amp problem. Lastly, check the fusible link. It's the smaller (but still pretty big) red wire from your positive terminal. Gently bend it down the full length and see if any points bend easily but feel crunchy. I've had them corrode inside of the insulation 8" from either end. This can cause lots of gremlins in your electrical system too.

[aw12345]

I got the wiring diagram and diagnostic info to repair it. But the old manual is outside and I am inside with the flu. Will scan the pages when I feel better.

[jokers4x4]

Thanks

Nutter bypass worked!!!!!! Idles better and started first try. thanks for the input guys.. If anyone can tell me why, might be expecting to much, but Now i am confused. Happy, but confused.

[aw12345]

The nutter bypassed the little computer that retards the ignition timing, when that thing takes a dump it eats up the signal from the pickup coil in the distributor. Hence it will not run since it doesn't trigger the coil anymore. Is not uncommon is why I suggested it. By the way just got done scanning 10 pages lol, you fixed it to fast. Will post them somewhere online might come in handy the next time you have an ignition problem. Here is the link to the pages

http://public.fotki.com/aw12345/cj7-ignition/

[jokers4x4]

thanks sorry. It wasn't fast enough for me. 6 days no jeep. AAAAAUUUUGGGGGGHHHHHHHH. I will down load the pages. I have found chiltons to be very limited over the years. took it for a Test drive after i got it running. wouldn't start at W-Mart, jumped it at the silenoid ran over my foot and almost hit a parked car. with my 7 year old in the car. And lost my leatherman ( that i used to jump it with) wasn't in park when it started. felt real stupid

[SAR Jeeper]

I think the Nutter Bypass only eliminates the computer control of the crappy Carter Carb.

Before:


After:


I would suspect your ignition module. Just about every time I couldn't get the Jeep to run correctly, it seemed to be that module. For about a month I was chasing a gremlin that would cut my ignition of I made a sharp left. Only if I made a sharp left. Ended up being my ignition module! Don't know how or why, but I changed it and now I can turn left!