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post #5 of (permalink) Old 01-07-2002, 11:14 AM
Junk Yard Genius
Join Date: Sep 1999
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Re: Mysterious engine

If you used the small red wire to the switch....
(Still, use the white wire as your grounded kill switch)

And this problem started after you installed the switch... I'd take the switch out of the circuit and see if the problem still exists.
You may have a bad switch.
If even a very tiny amount of voltage leaks through that switch, your MSD module will stay 'ON' ...
Staying turned on continuously will take it's toll on the unit.

The switch may be leaking to ground internally. (Something loose inside)
Wish I had a dollar for everytime I ran onto a bad switch....

You might also want to check for even the smallest tear in the insulation, so your voltage isn't going to ground somewhere...
Running wires through the firewall has a tendency to chew them up sometimes...
Even the smallest ground on the wire going to your switch would cause the problem you describe.

You may want to try some test procedures.

Connect a test light (any small light socket with two wires so you can put it anywhere...) to the red wire that originally went to the positive side of the coil.
One side to the ignition wire, the other to ground.
This will let you know if the problem is in the factory side of the wiring. Ignition switch, connectors, fuse box, ect...
If the light goes out when the ignition is 'ON', it's going to be a pain in the butt to track down!

If the Jeep dies, and the light stays on, then it's not the common ignition feed side of the circuit, and that rules out a lot of pain in the butt testing...

Next is the distributor input to the MSD module.

Check your connections! These operate at a few tenths of a volt, so anything in the connections will cause problems.
MSD doesn't have water tight connectors on anything but the Off-Road module, so that might be a worth while upgrade...

You also need to do a visual and Ohms test on the Hall Effect trigger. (replacement is $15)
But I suspect the wiring a lot more than the trigger.

While the ignition is throwing one of it's 'Fits', you can use the white wire to trigger the module.
Just 'spark' it against ground, and the module should fire the coil.
But with an intermittent problem, it's going to be hard to tell when the system starts working again....

So many cats, so few recipes...
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