91 cherokee... shutoff problems

[NotMatt]

91 XJ, 5 speed, 4.0 HO, etc etc. Pretty standard.

It doesn't shut off when I turn the ignition off. All the accessories turn off (radio, fan blower, etc), but the engine stays running and fuel pump stays running of course. I have to put it in gear and dump the clutch to shut it down, and disconnect the battery to avoid the fuel pump and ignition draining it if I'm going to not be driving it for a while.

I've pulled apart the column and fiddled with the ignition switch adjustment, hasn't seemed to fix anything. I've swapped the ASD relay with a known good one, still no change.

What else am I missing?

 

[junkyard jim]

Try unplugging the ignition switch. If it keeps running still, then unplug the power from the heater fan. If it still goes, then the regulator in the alt is sticking and feeding back to the ignition system OR a relay is sticking. (Did you do an MSD setup?)

 

[NotMatt]

So it's definitely not the ignition switch... the ****er just keeps on running when I unplug that. The fuel pump relay and ASD relay are both staying closed even with the key off, so something is grounding them out.

I hate wiring problems.

 

[MarcW]

Ill ask when James gets here in a few minutes. He had this EXACT same problem, and now his rig doesnt do it ????

 

[Qman]

It may be the starter relay on the fenderwell. My brother mentioned something about it on his '90. When I talk to him today I will ask.

 

[NotMatt]

It may be the starter relay on the fenderwell. My brother mentioned something about it on his '90. When I talk to him today I will ask.

'91 and later XJ's have a starter relay that is part of the underhood "power distribution center" or relay/fuse box. The PDC also has the auto shut-down and fuel pump relays, so maybe he's thinking of that. Either way, this isn't a starter relay problem... the starter works fine and doesn't stick on. The problem is that the ASD and fuel pump relays are closed all the time for some reason, so the fuel pump is running and the injectors have power to them even when they key is in the off position... which causes the motor to keep running even when the key is off.

If I disconnect the battery and reconnect it, the fuel pump primes and I can feel both relays click on. And no, they're not stuck or bad... I've swapped them with known good ones.

[EDIT]: I also swapped the PCM with a known good one as well, still no luck. I tore apart the PDC and didn't find anything fishy. The dark blue wire with yellow stripe coming from the PCM provides a ground for both the fuel pump and ASD relay as far as I can tell from the crappy Haynes wiring diagram....

Anyone know what the "service connector" looks like on an HO 4.0 in this year, and where it's located? I've never had to mess with this so called service connector, but according to the (again) shitty haynes diagram, if the service connector is shorted it would cause the fuel pump and ASD relays to stay closed...

I'm grasping at straws because I'm at my knowledge limit for troubleshooting electrical problems.... :haha: It isn't much of a big deal, cause I just put it in gear and dump the clutch to kill it... but it drains the battery over night to have the fuel pump constantly repriming and the ignition circuit on... :redneck:

 

[dumpsterdriver]

lol mine did that for a while, i ran two wires to the ecu fuse and would just twist them together to run and untwist for off:redneck:. then it just fixed itself when my high beam wires lit on fire and now the only thing that stays on is my warning lights (e brake, low range and that other stuff) and my low fuel light if im low on fuel. but the fuel pump isnt on anymore and she turns off again. ???. i figured it was the ign, but if it aint broke... i hope somebody knows what it is so i dont have to figure it out someday :redneck:

 

[dumpsterdriver]

my ODB connector is right above the pedals. what does that auto shutdown thing do? maybe it has somethign to do with it

 

[64FJ40]

Run a new power feed for the PDC with a toggle switch on it. Hide the toggle switch under the dash, but where you can still reach it from the driver's seat.

#1 - solves your run-on problem.
#2 - redneck theft prevention.




Or, just figure out why the PDC still has power when the ignition is off. If it's not the switch, I'd guess it's either a (very lucky) short in the harness somewhere or possibly the alternator like JJ said? I'd disco the alternator (or pull the belt for a minute) and see if the results are the same.

 

[NotMatt]

Run a new power feed for the PDC with a toggle switch on it. Hide the toggle switch under the dash, but where you can still reach it from the driver's seat.

#1 - solves your run-on problem.
#2 - redneck theft prevention.




Or, just figure out why the PDC still has power when the ignition is off. If it's not the switch, I'd guess it's either a (very lucky) short in the harness somewhere or possibly the alternator like JJ said? I'd disco the alternator (or pull the belt for a minute) and see if the results are the same.

I could pull the belt, but I'm doubting that will solve it. I guess I didn't make it too clear, I turn the key off and the rig keeps running. If I shut it off by pulling the ASD relay or just dumping the clutch, I can go pull the battery cable, re-install it, and the relays click back on and the fuel pump primes... so something is keeping them energized even after the engine is killed by some other method. It's not the alternator unless I have a new fancy one that generates current even when not spinning.

The problem also is not 12 volts at the PDC, as there is always voltage at the PDC... the hot side of the battery is hooked directly to it. The problem is that the other side of the relay is staying grounded even when it's not supposed to be.

Maybe someone can verify this for me... unplugging the ignition switch on the top of the column... should kill the engine, no? I may just be looking at a faulty ignition switch after pondering this over some more... but I'm uncertain how the engine should act with it unplugged... the more I think about it, the more I start thinking that once the motor is running, it will stay running as long as there is input from the CPS and other sensors and the ASD relay isn't deenergized... unplugging the switch itself shouldn't affect it?

I don't know, just talking out loud to myself I guess. I need a better wiring diagram of the ignition system, will have to track something down after work tonight.

 

[MarcW]

well, i thought james did something intelligent, but a simple dash fire seems to have cured the problem :haha:

 

[64FJ40]

I could pull the belt, but I'm doubting that will solve it. I guess I didn't make it too clear, I turn the key off and the rig keeps running. If I shut it off by pulling the ASD relay or just dumping the clutch, I can go pull the battery cable, re-install it, and the relays click back on and the fuel pump primes... so something is keeping them energized even after the engine is killed by some other method. It's not the alternator unless I have a new fancy one that generates current even when not spinning.

The problem also is not 12 volts at the PDC, as there is always voltage at the PDC... the hot side of the battery is hooked directly to it. The problem is that the other side of the relay is staying grounded even when it's not supposed to be.

Oh right. My reading skills are weak today. Carry on then.


I'm pretty sure I have a chilton's or hayne's manual for that year at home. I won't be home to look at it tonight, but if they aren't readily available online I'll look at the wiring diagrams for you tomorrow.

 

[TreeClimber]

Matt, does it have a GM style key? The ignition switch is at the bottom of the steering column, and is controlled by a rod from the key. I theorize, that it indeed could be caused by a bad ignition switch.

 

[NotMatt]

well, i thought james did something intelligent, but a simple dash fire seems to have cured the problem :haha:

This one has already had one dash fire... I ended up replacing pretty much everything on the passenger side, including the blower motor, wiring and dash itself. Maybe another will cure the problem. :redneck:

Matt, does it have a GM style key? The ignition switch is at the bottom of the steering column, and is controlled by a rod from the key. I theorize, that it indeed could be caused by a bad ignition switch.

Yeah it has the older style column with the rod. I had it all apart yesterday and did the whole testing/adjusting/etc on the switch, but I suppose the internals could still be bad. Wish I would've pulled it apart and looked at the inside while I had the column dropped down. Doh.

 

[Binder]

It could still be the key switch or starter relay depending on how the rig is wired. Could also be a short in a wiring harness. Without a schematic or someone who is familliar with that specific rig it's hard to tell for sure.

 

[junkyard jim]

Try switching the AC and heater to the off position then shut the rig off. Unplugging the regulator connector on the alt is easy.

 

[Avanteone]

That's an interesting problem Matt, I haven't seen that one before. My guess is that your theory is correct and it's a bad ignition switch... and once it's running, disconnecting it doesn't kill it because everything is already energized. Lemme know if you need any wiring diagrams and I can get 'em for you tomorrow.

John

 

[NotMatt]

That's an interesting problem Matt, I haven't seen that one before. My guess is that your theory is correct and it's a bad ignition switch... and once it's running, disconnecting it doesn't kill it because everything is already energized. Lemme know if you need any wiring diagrams and I can get 'em for you tomorrow.

John

One thing I didn't test because I didn't think of it... disconnect the negative terminal on the batt, disconnect the ignition switch, then put the neg terminal back on and see if the relays click on and the fuel pump primes... that would certainly tell me whether it's the switch or not.... if nothing happens, the switch is definitely the culprit. Didn't think of that while I had the column dropped, but tomorrow night I'll see if I can just reach the ignition switch plug without dropping the column and test it out.

If you have a page with a good diagram showing the ASD/fuel pump/ignition circuit that would be awesome.

 

[NotMatt]

Ok so it's definitely NOT the ignition switch... the fuel pump still primes even with it completely unplugged.

Man, I am not looking forward to tracing down a short in the harness somewhere. Maybe I'll just install an easily accessible battery cutoff switch and call it a day.

 

[NotMatt]

Try switching the AC and heater to the off position then shut the rig off.

I'm mulling over how this would be the culprit in my head... I can't see how it would cause the rig to keep running, as all the accessories (including the blower fan and radio) shut off when I turn the key off... just the motor keeps running. I guess everything's worth a try though at this point... :redneck: