electrical problem with an 86 CJ7

What was shorting the first time?

You could be describing a punky ground to the body of the Jeep. It could be a smaller black wire from the battery to the firewall or a mesh cable from the back of the head to the firewall.

Mike

Bill wrote:

Have you made sure the fule filter is not clogged? If the filter is getting plugged up, the motor can run fine at relatively low speeds, but miss alot at high speeds.

problem resurfaced. I would check for any wires especially plug wires that melted through by finding their way on to the exhause manifold resulting in shorting your spark to ground for one or more pistons.. A good visual for pinched/melted wires, or loose connections is probably a good idea. If that netted zero, I would pull the electrical module (I assume you mean ignition module) and take it in for testing. Most of the chain part stores have a test fixture for these.

If all that nets zero you will probably need some qualified help.>

Check the condensor (capacitor) across the points if you have one

I am getting this post as a 're' in a cross post from somewhere....

I don't understand how a tune up fixed a 'short' in the wires? Was a plug wire arcing out to the head?

When my 86 CJ7 starts missing, I check plug wires. The last time, the wire to #1 plug was loose. Pushed it back on tight and away I went.

Then I check the distributor cap. They are open to the air and get dirt inside them easily through the vacuum advance linkage hole. Then they arc out.

There also is a bad bunch of cap and rotor combinations out there! The rotor is too short for the cap making too big a gap so they start arcing out after not many miles. This causes a miss. The arcing will be visible when you open up the cap and look inside with a bright light for carbon tracks and built up crud on the contacts.

If all is fine there, then I change the gas filter. You have to be careful to get the gas filter in right side up. It has 2 outlets, the center one goes to the carb and the 'top' one goes to the return line. If the return line isn't at the top, gas can syphon back to the gas tank when it sits causing hard cold starts and misses when the filter starts to get old.

Then I check the coil connection. That crappy Ford coil clip fails often or just needs a good clean.

You also should/might have a condenser on the side of the coil. To see if this has shorted, just unplug the thing. It will run fine for a while without it. It is there to suppress surges to the ignition module and maybe as a radio filter.

Hope some of this helps,

Mike