1975 Jeep CJ-5 Ignition Help

I have a 1975 Jeep CJ-5 with the 258 Inline Six.

I have a question about the ignition, when I start it everything is fine, then when I turn the key to off it is still fully running, and I can't shut it off until I put my hand over the carb to suffocate it.

 

Sorry, First time here.

I have a question about the ignition, when I start it everything is fine, then when I turn the key to off it is still fully running, and I can't shut it off until I put my hand over the carb to suffocate it.
Can anybody tell me what I am doing wrong?

 

I know it has something to do with a diode...I think you can search that term and get the right threads. Or wait awhile and someone is surely to chime in.

I know this subject has come up in the last two months.

 

Untill you get it fixed properly, you can also put it in gear (3rd or 4th), and with your foot firmly on the brake, slowly let the clutch up untill it stalls....

 

The diode thing should not be needed if you have the factory wiring harness. If you need a diode, it's a problem encountered with the Delco alternators. They will back-feed the ignition through the exciter circuit unless something like the diode prevents it. Here's a diagram:



I recall that the factory installation uses a bulb as a resistance to prevent backfeed. The factory wiring diagram shows a resistance.

I'd expect you could easily test this by disconnecting the excite wire from the alternator and see if the engine still runs on.

 

Thanks, i haven't tried that yet. Would it matter if I have a Prestolite system?
I have 1 NEGATIVE wire going to the starter, also I don't have the Ballast Resistor installed, cause I was told that is for Ford and I didn't need to use it.

Also i have an aftermarket igniton switch so I had to cut the connector off and have a 4x4 place in town wire it up for me, could that be the problem?

Could it be the exciter wire and the red wire are backwards? Or do I need that diode between the exciter wire and the alt?
Also, what light bulb should i link it through?

 

You should have the ballast resistor in there right before the coil. But if you are running an aftermarket ignition like an MSD box, you would remove the ballast resistor and have to add the resistor diode just off the alternator.

I just went through the same thing with my MSD box.

As said earlier, putting it in third or fourth with your foot on the brake and dumping the clutch is easier than getting out and smothering the carb. Unless you have an auto that is.

 

well i have a Weber performence off-road carb on it and it is easier to just leave the filter off when i start it, and then just turn the key off and just suffocate it, cause i have it on jack stands cause of flat tires. Could put a battery cut-off switch in-line on the POS cable to the starter relay?

Also i don't have an MSD box, it is a Prestolite ECM/Starter Relay/Delco External Alt, i meant the ignition key switch is not the original one that it came with, i bought it through Auto Zone cause it was universal.

Also the wiring is not original, i recently put in a Painless wiring harness.

 

Painless=diode needed. At least on the ones I have seen.

 

Yes, you should not have this problem with the Prestolite ... However! A 1975 CJ-5 with an inline 6 comes with a Delco alternator, so you should have the Delco.

Possible.

The schematic is an example of where the diode goes, not an exact representation of your wiring. So, don't take it too literally.

The bulb is your "ALT" light on the cluster. When the alternator is running, the alternator holds the excite wire high. This makes the 12V from the switch balance the 12V from the alternator, so no light in normal operation. With the key on and the engine stopped, the excite connection acts as a sink for the 12V from the switch, so key on lights the alt light. If, say, your alternato belt breaks, the alternator again acts like a sink and the lamp lights, indicating alternator failure.

 

What about the ballast resistor?

Do I need both the diode and the ballast resistor?

Also does anyone have a pick of the diode installed?