Runs after Key is off

Runs after Key is off


Missing-Presumed Wheeling
Lifetime Supporter
Plumas Lake, CA, USA
1974 CJ5 ~ Fresh built AMC 360 - SM420 - D20 - D30F with upgraded 30 spline shafts and knuckles & D44R - 4.27 Gears - ARB Lockers F/R - All chrome molly axles - on 33's - YJ 4" Lift Spring Conversion
I mean actually still runs and will drive still (for little bit).

But not all the time.

I have modded the distributor (DUI), MSD ignition street fire box, new higher output alternator, have replaced recently the battery with red top optima, the starter solenoid, voltage regulator, and some misc wiring.

So from what I can tell, the alternator is pushing current back through the ignition circuit somewhere.


Start tracking the wiring from the alternator again, and see if I can figure out which wire is the cause? Should I need a "reverse flow" resistor inline the charging wire?

:chug: :notworthy:

~ JR
How do the spark plugs look? if you have too much timing advance, it will ping of course, and there will be deposits on the spark plugs that stay hot after engine shut off. I believe that the DUI can adjust maximum advance which should be around 28 degrees.
The "reverse flow resistor" you speak of is actually a "diode" but I will have to do a bit of hunting to see where you want to put it. It is, from what I remember something to do with the alternator exciter wire??:wtf:
I'm not sure how your MSD ignition works exactly. But the wire on the + side of my coil runs back to through the tach and straight to the ignition switch on the steering column. When you turn off the key it should completely cut the power to the coil. Maybe check your ignition switch.

Another though... through a volt meter on the + side of your coil and see what happens when you turn off the key. The voltage should go to zero.
Your ignition needs a diode installed on the SMALL wire at the alternator.

It is referred to as the "excite" wire, and it is the smaller of the two on the plug at the alternator.

I just put one on my Jeep. Part number 275-1143 from Radio shack. Its about $2 . It needs to be installed with the band TOWARDS the alternator. It keeps power from flowing "backwards" into the ignition circuit.

I yanked the coil wire to kill it once.... ONCE !!! BAREHANDED!!

Then I smothered the carb to kill it....

Then I actually FIXED it with the diode.
Thanks Guys.

This excite wire, is that the wire that puts a small amount of voltage to the alternator to "start" its production energy?

~ JR
Thanks Guys.

This excite wire, is that the wire that puts a small amount of voltage to the alternator to "start" its production energy?

~ JR
Yes it is.
A diagnostic test would be to have the Jeep running, turn the key to "off". Normally it would kill the engine. However since yours is still running, pull the plug from the alternator. If it dies, then that is what you need.


good luck.... And good luck soldering the diode inline. I couldnt get it to take solder, so I had to use inline wire connector with shrink tube after I crimped it.

Thanks guys. Going to get searching for the radio shack close by, and see if I can pick one of those things up.
Ignition switch or ground.
The link below is a write-up on converting to a Delco alternator. In the article is a part number for the diode that is available at most auto part stores. There is also an explaination of the why the Jeep will continue to run without the diode.

Delco Alternator Upgrades - Jeep-CJ Documents and Manuals

I realize this is an older post, but hopefully it will help someone else with the same issue! :D
Thanks Dunebuggy!

I forgot to finish out the thread. The diode worked like a charm!

Ended up picking it up at the local radio shack

~ Jr

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