How to adjust for dieseling / engine run on?

[PatrickRyan]

1978 CJ5 with AMC 304
Motorcraft 2100 carb
MSD 6AL analog ignition

Setup ran fairly well. But starter has been iffy for a while.
Then, 2 weeks ago, Jeep refused to start. No cranking, etc. Just dead key.

I was able to jump across the solenoid on the fender. The starter was fine. The solenoid was the culprit. Didn't have time to mess with it. Real life stuff.

So this past Saturday, I finally had the time to fix it. (I know, all of five minutes lol)

Anyway, I replaced the solenoid with a $28 part from NAPA.

The engine just cranks right up. It runs smoother than ever. It's great. Except, now, the only way to kill the engine after it warms up is to pop the clutch.

If I turn the key off, it never even sputters. Just keeps churning along like I never did anything. I'm sure that I could probably drive the thing if the steering wheel didn't lock up.

This is a completely new behavior. I'm not sure what I did that would have caused this. All I did was disconnect the battery, replace the solenoid and re-connect the wires. No adjustment on the ignition or carburetor.

Any ideas?

 

[Lumpy Grits]

Check your ign timing.
LG

 

[Scout1067]

Does it have an electric fuel pump? If it does, it will keep running until it's empty. I bet it's an ignition switch fault. Soundsto me like the engine is still getting electricity after you turn off the key.

In the Army when our Bradley's were topped off we could shut off master power and fuel would gravity feed so the engine would keep running. To kill the engine we had a manual fuel shutoff switch.

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[PatrickRyan]

Does it have an electric fuel pump? If it does, it will keep running until it's empty. I bet it's an ignition switch fault. Soundsto me like the engine is still getting electricity after you turn off the key.

In the Army when our Bradley's were topped off we could shut off master power and fuel would gravity feed so the engine would keep running. To kill the engine we had a manual fuel shutoff switch.

Sent from my ALE-L21 using Tapatalk

No sir. Mechanical pump.

Thank you for your service.

 

[Scout1067]

No sir. Mechanical pump.



Thank you for your service.

It was a thought, the entirety of my experience with diesels is Bradley's, 113s, HMMWVs, and the old Massey tractor on the farm growing up.
Hope you figure it out and it's an easy fix.

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[JR74CJ5]

I'm guessing the solenoid you just replaced is the culprit. If you changed nothing else, and this is new, then that's the issue. Double check you got all the wires to the correct spots. If you did - it may be faulty with a "wire crossed" internally. Test or bring back to Napa to test.

Am I correct in assuming everything was running fine until the no start solenoid replacement? Turned on and off with key like normal after the MSD ignition wiring? If not, then you have power backfeeding the ignition circuit through the MSD etc. Wiring mistake, or need a diode (backfeed blockage).

From there, it could be something in the ignition switch shorting over.

If you did anything else different between when it didn't do it to now when it does, let us know. Alternator wiring can cause this, but if you didn't change it, it's not the culprit.

Double check all your wiring with a multi meter if you have one. Post some photos if you want to might help.

I think you either got a wire crossed while installing the napa solenoid, or while installing the MSD box, or bad solenoid out of the box.

Have the old one still? Put it on, jump start jeep with Key on, turn key off, does it still do it or shut off normally - if so, it's the new one internal, and not your wires... 99% (unless I'm missing something...)

Lumpy I don't think it's a timing run on, although after this upgrade i would check timing, sounds more like backfeeding ignition to me right? if timing dieseling it would surge / chug. Ignition circuit is getting power still while key off.

 

[JR74CJ5]

Could still be your ignition switch went bad at just the wrong time too, but I'd bet on my above...

 

[PatrickRyan]

I'm guessing the solenoid you just replaced is the culprit. If you changed nothing else, and this is new, then that's the issue. Double check you got all the wires to the correct spots. If you did - it may be faulty with a "wire crossed" internally. Test or bring back to Napa to test.

Am I correct in assuming everything was running fine until the no start solenoid replacement? Turned on and off with key like normal after the MSD ignition wiring? If not, then you have power backfeeding the ignition circuit through the MSD etc. Wiring mistake, or need a diode (backfeed blockage).

From there, it could be something in the ignition switch shorting over.

If you did anything else different between when it didn't do it to now when it does, let us know. Alternator wiring can cause this, but if you didn't change it, it's not the culprit.

Double check all your wiring with a multi meter if you have one. Post some photos if you want to might help.

I think you either got a wire crossed while installing the napa solenoid, or while installing the MSD box, or bad solenoid out of the box.

Have the old one still? Put it on, jump start jeep with Key on, turn key off, does it still do it or shut off normally - if so, it's the new one internal, and not your wires... 99% (unless I'm missing something...)

Lumpy I don't think it's a timing run on, although after this upgrade i would check timing, sounds more like backfeeding ignition to me right? if timing dieseling it would surge / chug. Ignition circuit is getting power still while key off.

I'm sure this is what I did. Honestly, I was not paying attention when I disconnected the wiring on the solenoid. Everything was running properly
before I swapped the solenoid. The MSD was installed when I bought the jeep. I'm sure I wired something wrong on the solenoid. Just not sure which wire is the culprit. The Only wire I have on the output side of the solenoid is going to the starter.

 

[JR74CJ5]

Is it a 4 terminal like this?



If not, show me what it is with link or napa part number...

 

[PatrickRyan]

Is it a 4 terminal like this?



If not, show me what it is with link or napa part number...

Yes sir. That is it. Or similar. 4 terminal.

 

[JR74CJ5]

As orientated in picture above, left large post should be battery, and / or any always "hot" 12v power needs. The starter cable is along on the right large post, which leaves the two center posts.

The right center post "S" terminal, should really only be the wire coming off ingnition switch (or maybe your control box) hot in "start" position I believe, but it's been a while singe I have the MSD box (mine died while submarine racing the jeep as members here called it.. ) Basically it's the signal terminal to activate the solenoid to pass battery power direct to the starter.

That leaves the "I" terminal for usually voltage regulator yellow wire if memory serves me, and possibly some ignition source power (keyed).

Now with the MSD, there may be a few changes from that. What all is going to what posts on yours?

 

[PatrickRyan]

I'll have to wait until I get off to go check. Thanks for all your help.

 

[JR74CJ5]

No problem bud.

If it get's "different" than my basic explanations, try to find a wiring schematic for the MDS box, and trace what each wire does and where it goes. I'm thinking your ignition control (MSD) switched power may be on your always hot lead. So when key on start it works, but shut off doesn't kill the signal to box and continues to send spark signal (keeps running). If so, it's got a pretty big ring terminal on it to get switched from the "I" terminal to the batt terminal... Did you have to cut anything for the new solenoid and rewire? Or just unscrew the nuts and replace?

Make sure there's a good ground between the casing of solenoid and body (the bolts normally - clean the holes up etc) grounds cause funny things to happen as well, though I don't think it's your issue, it won't hurt while you're at it...

If you can't figure it out, take lots of photos of the solenoid wiring, the MSD wiring, and the distributor / coil wiring etc.

Note where each wire is running to now, and we'll see if we can diagnose a bit more tomorrow or late tonight. I'll be doing some jeep work of my own after work, so will probably not be on here until tomorrow morning. (Stupid carb adapter vac leak...)

 

[PatrickRyan]

The only wires it can be are on the larger terminals. The 2 wires on the S and I posts have boots on them. Not sure the proper name for them. Looks like spark plug wire ends soldered on.

 

[Lumpy Grits]

Wonder if it's 'feedback' via the altenator.......
I had to do the Diode install deal in the wiring coming from the alt when I did my install.
LG

 

[JR74CJ5]

What do those two wire go to?

You should be able to rule out the starter lead, it should be by itself.

Happen to get any photos?

 

[PatrickRyan]

There are currently 7 wires going to the solenoid. The small red and blue wires coming from the loom running from the firewall on the driver's side. They are booted and go to the triggering terminals in the center of the solenoid.

There are also 2 thick red wires under the same ring terminal, also coming from the loom going through the firewall on the driver's side.

The slightly smaller red wire is coming from the MSD box.

There is also a very thick red wire coming from the positive battery terminal. And the last wire is going from the solenoid to the starter itself.

If the red wire going to the MSD box isn't on the always hot side, then the solenoid will not fire when ignition key is turned to start.

If the 2 solid red wires (under the same ring terminal) from the wire loom
are not on the always hot side, then the starter will try to crank the engine, but the engine will not run.

The only way that the engine will crank and run is if all the wires (other than the wire going to the starter from the solenoid) are always hot.

However, in this configuration, the engine will not die when you turn off the key.

I have noticed that if the engine is cold, then the run on may or may not happen.

 

[JR74CJ5]

Did you get a chance to look up the MSD wiring instructions anywhere? Start there. There has to be a switched power wire to that thing, as you would not want it completely always hot, it would quickly drain your battery. Think of like a radio - they have the memory always hot wire, and a switched power wire, so when wired up correctly you might see the clock display and your stations and settings are all good (unless you unhook the battery right?), but can't play the radio when key off. Or a relay if you're familiar with them, it may have a always hot lead, but it would have a internal relay basically that would only activate the controller when key on.

The first step I'd do from here is find those instructions. There may be a wire that does need a diode installed in it, but if that is the case it should have been doing this, or trying to do this, since the MDS box was installed...

To confirm, the power in from battery always hot is the large left post closer to the "I" terminal on yours right? The large to starter cable on the right next to "S" terminal right? If so, continue below. If not, yours is set up differently, so it's going to be different...

I assume when you say below that the small red wire going to MSD box is not on hot engine won't fire, you tried putting it on the "I" terminal for the test (or another switched power source)? It didn't work? Having it completely unhooked would definitely cause nothing to occur.

One pre-test. Take it back off the always hot (MSD wire), and leave everything else as it. Temporarily put it on the always hot (make it easily removable, safely with alligator clip, hold it there, etc) have someone start the engine and turn it off and get it to do the issue where it's still running with key off. Now pull that MSD box always hot wire. Does it shut off? If so, try it on switched power instead, and I would bet your fixed...

If not:

remove the large lead to starter once unhooked (I want to ensure you don't run over your own foot... I damn near did the other day - thought it was out of gear! lol), and everything else hooked up try these tests)

If you have a helper, and a voltmeter:

Ground the black prong to battery post and test continuity between it and the mounting bracket of the solenoid. Should show good connection closed loop. (Mine beeps and shows 1 I think?)

Now, leave black on battery if you can, or bracket if confirmed getting good ground and test voltage as follows.

Should have 12v at the large left terminal closest to "I" terminal.

Key off - test the "I" terminal - should be nothing. Key on should be 12v.

Key off - test the "S" terminal - should be nothing. Key on, should be nothing.

Key off - test the large right terminal - should be nothing, key on should be nothing. Only should have something when key in the start position.

Once all that is confirmed, we've ruled out a bad solenoid mostly:

Let's try this. I assume your alternator is a externally regulated one. If so, remove the wires going to the exciter post on the alternator. Hook back up the large starter wire to solenoid, and start it. Shut off key. Does it work now? If so, lumpy is correct above, but I have no idea how it wouldn't have done this before you changed the solenoid... The exciter wire should be hot when ignition is on, and tells the alternator to get it's butt in motion and make juice! So it's common that it will backfeed poser back to ignition circuit if you don't have a diode or the "amps light" hooked up to block backflow.

Past that I'd be at a loss unless I can see and test it personally in front of me... Or knew exactly how your jeep is wired...

But something is feeding voltage to the ignition circuit while key is off if the issue...

I'll keep an eye on this best I can, but usually am not on a whole lot over the weekend. Let me know if you have questions though.

 

[PatrickRyan]

I got it fixed. Just not sure what the problem was. I started from the beginning. I disconnected everything from the solenoid and the MSD. I hooked the power leads from the msd directly to the battery. The hot was hooked to the always-on side of the solenoid. It is now directed to the battery. The ground was under the same lug on the block that the ground from the battery was connected. I removed it and replaced it directly on the negative terminal of the battery.

I also removed and replaced/resoldered all the terminals on the wires.

I reconnected everything to the solenoid. Everything is as it should be. Runs and cranks and dies as it should.

I love chasing ground problems on my jeep. It is the best.

 

[PatrickRyan]

Ran fine for a couple of days. Shut it off to fill the tank this morning on the way to work. Wouldn't start at the pump. Let it sit a while. Turn over but not start.

Got out of the jeep. Cussed a lot and got a little mad.
Got back in the jeep and it started up. Got to work, and what do you know. Won't cut off again. So back to popping the clutch to kill it.

I'm starting to think the MSD box is starting to go. But I'm not sure and I hate spending the money on maybe.