Engine runs with key removed?

[DAA]

Need some help troubleshooting an issue that came up last night with my Son's '95 ZJ 4.0.

The battery was dead so we jumpstarted it. Then drove it a little while and when we got home and he turned the ignition off and removed the key, the engine kept running. If I'm remembering right, the accy's all turned off when the key was removed, just not the engine.

Didn't have any time to mess with it, so I popped the hood and removed the neg. batt cable but that didn't slow it down at all. So I removed the pos. cable too. Nope, that didn't kill it either. Still running with no key and no battery. I grabbed the throttle linkage and it would rev up just like normal - this wasn't just some extra heavy duty run-on. Dang thing just didn't want to die.

So I pulled a relay marked "auto shutdown" and that finally stopped it.

My first thought is ignition switch. But, I don't know how to troubleshoot it to make sure, before I go tearing the column apart and all that happy stuff.

Anyone have any ideas what besides the ign. switch this could be? Or can help me with troubleshooting steps to pin down the problem?

Any help greatly appreciated!

- DAA

 

[1995zj]

Sounds like ignition switch to me.

Removing the battery cables to try and kill the engine wouldn't work on any vehicle I can think of. The alternator is what powers the vehicle while it's running. The battery is just there to start your vehicle each time.

 

[zukking01]

Once the vehicle is started removing the battery would not kill a healthy vehicle, this is because the alternator charges the system and dumps the excess to the battery.

When you remove the key and the engine will not die it is because the kill wire has been reversed on the alternator. The 2 wire plug common on all alternators is most likely reversed.

Start it up with the autoshutdown relay and battery in place and while it is running pull the leads off the battery, it should still run.
Next pull the pig tail out of the alternator and it shouuld die, this will let you know the wires are reversed.

 

[jackjoh]

Makes me wonder how the wires got reversed.

 

[DAA]

The alternator wires can't be reversed. It had been running and turning off just fine until last night.

I'm wondering if somehow the jump start fried something? If it is just the switch, maybe that's what killed it?

Is it possible for anything OTHER than the ignition switch to be at fault here? Other than reversed wires on the alternator?

If it pretty much has to be the ignition switch, that's kind of good, I guess, since at least I know what it is and it isn't too expensive. I'd just like to be more sure that's definitely the problem before doing it. But I don't know how to troubleshoot it.

- DAA

 

[iamsparticus]

Did you try and start it the next morning? It is possible for gas engines to start diseling, had it happen on a 351 cleveland when too low of octane was put in but if the engine has alot of carbon build up it is possible but not as likley. Try starting it again and see if it does the same if not, then go get a ignition swith from the junk yard and put it in see if that works

 

[4554x4]

I installed an engine in a wrangler recently that had a Hesco fuel injection kit on it. It came to me with some extra pieces that were purchased for the swap that included a diode that had to be installed in one of the alternator wires to prevent continuious running. Untill I installed the diode, it would stay running with the key shut off. Perhaps your Jeep has a diode in it that has gone bad?

 

[DAA]

It definitely wasn't dieseling.

Something in the alternator, could be - again, maybe fried by the jump start? I just don't know enough about electrickery.

Would like to figure it out before just thowing parts at it though, that's for sure.

- DAA

 

[I Lean]

Disconnect the alternator, then start and run it on just the battery. If it shuts off properly, you'll know it's something with the alt. If it's the same as before, then it's your key switch.

 

[DAA]

That sounds like a plan. Thanks Carl!

- DAA

 

[DAA]

Well, whatever it is, it's intermittent. Working fine now and all I did was put the relay back in and hook the battery back up.

Oh well. Next time it happens I'll try disconnecting the alternator.

Makes me think ign. switch even more though. Don't think a fried diode or a fried anything else would be intermittent. But a switch...

- DAA

 

[Darwin]

if it happens again the remote keyless entry module could be a problem according to identifix

 

[jackjoh]

I think I would start wondering about your computer module.

 

[DAA]

It doesn't have keyless entry, so at least that's one thing I don't have to worry about.

Wondering about the PCM is about all I could do about it, too, I'm afraid. Wonder, that is. It's all mumbo-jumbo to me once "the box" is involved. So, I sure hope it ain't...

- DAA

 

[iamsparticus]

If it is a computer problem it most likley would of thrown a code by now and had other problems. even OBD 1's are smart enough to do that. If it happens again i would try replacing the ignition switch before the PCM, but pm to im pretty good with engine problems and i have access to manufracture info and tools also