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strange shutdown problems 79 cj5

2138 Views 7 Replies 2 Participants Last post by  cjjunkie
Jeep shuts down from belived ignition problem. It just stops running ant any time. No pattern has shown its ugly head. This has been going on for six months.
Very intermitten but seems to be increasing with time. I have replaced the ignition swith, the coil, and checked all wires. Only other part might be the ignition box which is very expensive. If any one else has had this problem or know of something that I may be overlooking the help would be greatly needed.

79 CJ5 258 firecracker red
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This happened to me alot with the 304. The wires to the ignition box take alot of moving and will crack on the inside. Start your Jeep and grab the harness and move it all around. I bet you will find your problem there. I ended up cut out and replacing the wires to and from the distributor, ignition box and coil, they had "dry rotted"
Ensure that the box has a good, I mean maybe straight to the battery, ground

I had the same problem on both my 1978 CJ-7 and my 1985 CJ-8 - both with 258's. Check to see of the ground side of the coil
has a plastic connector about three inches from the coil connector. If it does, this may be the problem. I have not found any
purpose for this connector (maybe AMC diagnostics or something) but it will sometimes not make a good connection. It will drive
you crazy. I spent most of a summer not wanting to go too far from home because of this problem. I replaced the connector
with a butt splice connector and my troubles went away. The other problem that I found is that the coil wire to the distributor
sometimes does not make a good connection in the coil or the cap. Chack this also. Email me direct if you need any additional pointers.

A conclusion is simply the place where you got tired of thinking.
Hello Stephen,
The module you have in your Jeep, if it hasn't been messed with, is the Motorcraft DuraSpark ignition module. It is the same 'Blue Grommet' module that was used from 1976 to present. The local discount auto parts store has them from $16 to $35 dollars depending on manufacturer.
If you are sure it's not a fuel starvation problem, and is the ignition system, the I suggest you just go to the local 'auto-jerks' and pick up a module for a '79 Jeep or '79 Ford anything, particularly Ford pick-up trucks. (Auto Zone, Auto Works, Advantaced Auto, Car Quest, Big 'A', Ect., Ect....)
It doesn't matter if it's for a V-8 or I-6, they both use the same module.
If this doesn't take care of the problem, let me know, and I'll tell you how to wire the new module so it does work, independent of the stock wiring harness.

Hope this helps, Aaron.

So many cats, so few recipes...
I had a very similar problem with my '77 304. Everybody I went to said it was ignition "D*** prestolite ignition) so I replaced the module ($70) checked the wiring, jumpered over questionable wires, etc... it WASN'T the ignition. It was the fuel pump! Its a standard ford pump, is about $12, and is easy to get at on the 258.

Does the jeep want to start after it died? If not, try putting a splash of fuel down the carb. That would 'prime' the intake and sometimes spin the engine fast enough for the pump to start supplying fuel again...
remember to replace the filter whenever you do something to the fuel supply system... /wwwthreads_images/icons/smile.gif

Florida Mud CJ-5
'77 RB304, t-150 D20 4" 35" swampers
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A fuel starvation is easy to tell....the engine will loose power but not die instantly. If its dies instantly, then its ignition related. The possible causes are listed in order of most common to less common.

1. Duraspark module. As noted above, not very expensive. The fact that its getting more frequent suggests this module. Heat is a common cause of failure. If you put a voltmeter on the neg term of the coil, you can measure the voltage. If it goes above 6-8 volts then its the module. Usually, at about 8-9 volts the engine will die. The HEI mod will bypass the module and give you a better running engine.

2. Wiring. A wiring problem will usually be noticed when you go over a bump. Do the pull and shake on all the wires to see if one of them kills the engine.

3. Coil. Either it works or it doesn't. The most common problem is for heat to cause a bad connection to open up. You can use a hair dryer to heat it up.

One last thing to check is the connections for you tac if you have one. The tac has 2 heavy gauge wires going to it. If you unplug them the engine will not run.

Let us know what you may help the next guy.

John......southern CA
84CJ7, 3"lift, 32"BFG, 4.10's, ARB Locker, Solid Axle's, Durabak
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I may have fixed it. I took the advice of getting a control box and found out it was only 20 with tax to my supprise. Thanks for the advice it has been wheeling about 3 hours of driving and not once has it quit.

79 CJ5 258 firecracker red
I had a similar problem ,it would work fine and unexplainably quit!
After taking sometime and verifying systems the problem was found in the connector for the steering column to the main harness.
Overtime it had developed corrosion in the connections ,after a good cleaning it has worked fine.
just another thought !

Keep the shiny side up !
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