91 HO Shut Off While Driving

[schardein]

On 8/27/2021 at 3:30 PM, kryptronic said:

A bad camshaft position sensor (CMS) would cause rough idle, not a shutdown.  Plus I replaced the distributor last year, which contains the CMS, and the CMS is new.  Rule out the CMS.

The camshaft sensor in my 91 XJ would cause a hot shut down.  When it cooled off, the truck would start and run again.  I first thought it was a crank sensor, as that had been my previous experience.  Also, due to unrelated wiring problems, I couldn't use the "key-on-off-on-off-on" and count the flashes of the check engine light to get the trouble codes from the computer.  When I repaired that wiring, I was able to see the computer was throwing the code for the camshaft sensor.  I replaced the distributor with a later model one (as others have suggested in this thread) and it cured the problem.  Another nice thing about the later distributor is the sensor is replaceable without disassembling the shaft from the distributor housing.  Makes it very simple to carry a spare sensor and replace it as a quick test.

 

[Tex06]

On 9/20/2021 at 7:39 PM, omega_rugal said:

 

we probably should start putting coolers to manuals transmisions too.. and differentials can get hot under load...

 

They're actually pretty common in the performance world as are differential coolers. Typically Jeeps don't need such things because the low RPMs that both the tranny and the rear end see.

Trans-Cool NV4500/NV5600 Manual Transmission Cooler (genosgarage.com)

 

 

[acfortier]

So, I ended up replacing the coil with a yellow Accel unit, but still having random shut down/restart issues. Had it idling in the driveway to get it up to temp, and it shut off as if someone just turned the key off. Didn't sputter or anything, just died. Went back in and turned it on again without issue, and stayed idling for the next 30 minutes or so.

 

Today, while getting an inspection sticker, it wouldn't start. Just kept cranking and cranking and cranking. We had to push it out of the bay, and after letting it sit sometime while continuing to try to get it to start, it finally did.

 

I'm not entirely sure if this sounds like a CPS issue? I know @kryptronic did a lot of work to the fuel system, but something still doesn't seem right.

 

When the key is in the ON position, is it possible to hear the fuel pump? I did notice that while it was in the ON position, I couldn't hear anything from the fuel tank while I had my ear next to the fuel door.

[kryptronic]

15 hours ago, acfortier said:

When the key is in the ON position, is it possible to hear the fuel pump? I did notice that while it was in the ON position, I couldn't hear anything from the fuel tank while I had my ear next to the fuel door.

 

I was hoping that coil fixed your issue.  I wonder at this point if the new distributor has a faulty cam position sensor.  PM me if you want me to ship you the OEM unit I pulled from the truck.  I still have it.

 

The fuel pump will prime itself when you turn the key as lomg as it's not already primed (it will stay primed for about 5 minutes).  You should hear it.  

[acfortier]

4 hours ago, kryptronic said:

 

I was hoping that coil fixed your issue.  I wonder at this point if the new distributor has a faulty cam position sensor.  PM me if you want me to ship you the OEM unit I pulled from the truck.  I still have it.

 

The fuel pump will prime itself when you turn the key as lomg as it's not already primed (it will stay primed for about 5 minutes).  You should hear it.  

Me, too! I can't remember--did you proactively replace the dist. or was there something else going on? I see @ghetdjc320 is suggesting to go with a 94+ dist., which I should be able to find OEM used, or aftermarket. Not sure if one way makes more sense than the other.

 

Hmm, OK--it may have already been primed the first time, which is why we wouldn't hear it the others.

[ghetdjc320]

23 hours ago, acfortier said:

So, I ended up replacing the coil with a yellow Accel unit, but still having random shut down/restart issues. Had it idling in the driveway to get it up to temp, and it shut off as if someone just turned the key off. Didn't sputter or anything, just died. Went back in and turned it on again without issue, and stayed idling for the next 30 minutes or so.

 

Today, while getting an inspection sticker, it wouldn't start. Just kept cranking and cranking and cranking. We had to push it out of the bay, and after letting it sit sometime while continuing to try to get it to start, it finally did.

 

I'm not entirely sure if this sounds like a CPS issue? I know @kryptronic did a lot of work to the fuel system, but something still doesn't seem right.

 

When the key is in the ON position, is it possible to hear the fuel pump? I did notice that while it was in the ON position, I couldn't hear anything from the fuel tank while I had my ear next to the fuel door.

Have you tried replacing the ASD relay in the power distribution center. Or fuel pump relay also? 

[acfortier]

Just now, ghetdjc320 said:

Have you tried replacing the ASD relay in the power distribution center. Or fuel pump relay also? 

I have not--would those intermittently fail? I can snag a few from the auto parts store and swap them out, easy and cheap enough.

[ghetdjc320]

10 minutes ago, acfortier said:

I have not--would those intermittently fail? I can snag a few from the auto parts store and swap them out, easy and cheap enough.

If either of those the relays are failing intermittently that could cause the issue. Other issue could be the ecu connector. You can try removing it, cleaning it all out and reinstalling. 
 

The ASD circuit basically feeds power to the injectors and coil so the ecu can control the ground side pulse.

[kryptronic]

On 12/8/2021 at 12:54 PM, acfortier said:

Me, too! I can't remember--did you proactively replace the dist. or was there something else going on? I see @ghetdjc320 is suggesting to go with a 94+ dist., which I should be able to find OEM used, or aftermarket. Not sure if one way makes more sense than the other.

 

Hmm, OK--it may have already been primed the first time, which is why we wouldn't hear it the others.

 

I had multiple issues at once which caused problems for me.  First, the intake host for the fuel pump in the tank came loose so I basically ran out of gas when the fuel level went too low as the pump couldn't pump the gas.  When I fixed that issue the truck came back running rough.  I replaced the distributor at that point (for good measure).  But then I discovered a bad O2 sensor and a crushed downpipe which were the real culprits for the rough idle.  The distributor was likely fine.

 

So there was nothing wrong with the distributor when I replaced it.  I did have a hell of a time indexing it, though, as the timing marks on the harmonic balancer do not line up correctly when cylinder one is at TDC.  I think the balancer has turned over time (remember I noted it was near end of life), making the timing marks inaccurate.  It happens.  If you yank the distributor, DO NOT rely on the timing marks - find TDC by probing cylinder one.

[acfortier]

3 hours ago, kryptronic said:

 

I had multiple issues at once which caused problems for me.  First, the intake host for the fuel pump in the tank came loose so I basically ran out of gas when the fuel level went too low as the pump couldn't pump the gas.  When I fixed that issue the truck came back running rough.  I replaced the distributor at that point (for good measure).  But then I discovered a bad O2 sensor and a crushed downpipe which were the real culprits for the rough idle.  The distributor was likely fine.

 

So there was nothing wrong with the distributor when I replaced it.  I did have a hell of a time indexing it, though, as the timing marks on the harmonic balancer do not line up correctly when cylinder one is at TDC.  I think the balancer has turned over time (remember I noted it was near end of life), making the timing marks inaccurate.  It happens.  If you yank the distributor, DO NOT rely on the timing marks - find TDC by probing cylinder one.

Ah, makes sense. Well, if you want to send the old distributor my way, let me know how much $$ you'd like for it.

 

I did end up replacing the ASD relay but haven't had the chance to drive it far enough to have it happen again. I did get a spark tester that I can clamp somewhere so I can hopefully see through the hood if I'm by myself and it dies again.

[gogmorgo]

Not necessarily relevant to the issue at hand but to the discussion, for anyone who might stumble across this thread from a Google search or something; when I swapped out my first MJ’s original distributor a long time ago I also had a heck of a time getting the new one indexed. I recently reused that “new” distributor in another project, and same thing, but during the process this time I noticed the oil pump drive and rotor drive are clocked differently relative to each other than they were on the original unit. Just something to watch out for with aftermarket parts.

To the issue at hand, an intermittent total shutdown with a no-crank could potentially be a crank sensor issue, yes. The giveaway would be complete loss of spark. I’d look carefully at the wiring to it and make sure it’s properly seated in its hole before replacing it. You should be able to see a small a/c voltage coming off it while disconnected and cranking the engine over if it’s working properly.
 

As far as the fuel pump is concerned, when you turn the key on it should run for a few seconds then shut off. 

[kryptronic]

On 12/27/2021 at 8:18 PM, acfortier said:

Ah, makes sense. Well, if you want to send the old distributor my way, let me know how much $$ you'd like for it.

 

I did end up replacing the ASD relay but haven't had the chance to drive it far enough to have it happen again. I did get a spark tester that I can clamp somewhere so I can hopefully see through the hood if I'm by myself and it dies again.

 

If the ASD relay doesn't solve it, I'll send you the old distributor for the cost of shipping.  Just PM me and I'll get an email alert and will get back to you right away.  I've been busy lately and haven't checked the forum much and I have to be on here to get post notifications.

[acfortier]

Well, drove it ~50 miles yesterday and didn't have any issues whatsoever. Hoping that it was the ASD relay all along.

[kryptronic]

On 1/3/2022 at 10:47 AM, acfortier said:

Well, drove it ~50 miles yesterday and didn't have any issues whatsoever. Hoping that it was the ASD relay all along.

 

Awesome!!!  My fingers are crossed.

[ghetdjc320]

On 1/4/2022 at 1:47 AM, acfortier said:

Well, drove it ~50 miles yesterday and didn't have any issues whatsoever. Hoping that it was the ASD relay all along.

Great to hear! Hopefully that was the culprit but if not, the list gets smaller and smaller from there.

[acfortier]

Well, this reared its ugly head again. Went to go pull it out to do an oil change, and started to creep forward, then died. Definitely didn't stall it, just shut off completely. Went to go start it, and nothing. Will crank and crank and crank.

 

I had purchased this spark tester a while back: https://smile.amazon.com/gp/product/B0002STSBM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 and it looks like I'm not getting any spark from the ignition coil. I moved the needle from 40 kV to 25 kV, and it didn't make a difference. Nothing would appear. Unless I had a poor ground--I had it clipped to the metal lip where the firewall and hood meet, so I think it should be sufficient.

 

Not sure what to try and replace next, will have to go back through this thread.

[War_Pony89]

Acfortier, I'm feeling your angst. Most of what has been said started happening two days ago out of the blue. Idling while figuring out if soccer practice got cancelled, it just died. Started next day, when I went back first crank.

I found same thing, let sit, starts up. Has not died while driving but today after getting gas and going to walgreens would crank but not start.

 

I had noticed upon my first re-start the fuel pump was noticeable. When It died at the soccer field, I let pressure out of the line a couple times to make sure not a fuel pump. However, I did not recall hearing it prime again at that time. After cranking for few minutes, no fuel in the exhaust smell either which seemed odd given the number of cranks I put it through.

 

I know there is a lot of grounds to check, which I cleaned all last year when I replace the fuel pump with the Bosch unit. I'm going to chase the fuel presser pump issue first thing I get it back home.

 

Anyway, thanks y'all for contributing, I have my list from the article to go through.

[War_Pony89]

On 8/9/2022 at 8:05 PM, acfortier said:

Well, this reared its ugly head again. Went to go pull it out to do an oil change, and started to creep forward, then died. Definitely didn't stall it, just shut off completely. Went to go start it, and nothing. Will crank and crank and crank.

 

Not sure what to try and replace next, will have to go back through this thread.

AC,

 

Hope your project is progressing, i found it is not the fuel pump installed last year. Working great, PSI checks out. However on the Cherokee forum and I think here I saw it too. If the CPS is going out, it will cut off the spark to the coil and distributor. I can start mine when cold, Ohms check out, but when the warmed , I can't restart. At least that is my guess, cause ohms when warm is zero. So replacing my Crankshaft PS and will post updates, once I find my 1/2 to 3/8 adapter.

 

 

[acfortier]

30 minutes ago, War_Pony89 said:

AC,

 

Hope your project is progressing, i found it is not the fuel pump installed last year. Working great, PSI checks out. However on the Cherokee forum and I think here I saw it too. If the CPS is going out, it will cut off the spark to the coil and distributor. I can start mine when cold, Ohms check out, but when the warmed , I can't restart. At least that is my guess, cause ohms when warm is zero. So replacing my Crankshaft PS and will post updates, once I find my 1/2 to 3/8 adapter.

 

 

Yeah, I think that's going to be next on my list to change out.

[War_Pony89]

CPS is replaced, took 2.5 hrs. Ended up taking off the cross member and lowering the drivetrain 2 inches to make room.

 

Question for anyone, I removed my external slave cylinder to have room to swing the ratchet.I put it in and had no clutch pressure. When I pulled it off again the slave cylinder exploded. Is there an end cap on the end under the dust boot? Seems like there should be and I think its in the bell housing? Can anyone confirm this?

[gogmorgo]

I've done this while bench bleeding the clutch. Make sure everything is nice and clean and push it back together. The only thing keeping it in place is the pressure from the clutch fork, and the plastic strap while it's not installed.

[War_Pony89]

21 minutes ago, gogmorgo said:

I've done this while bench bleeding the clutch. Make sure everything is nice and clean and push it back together. The only thing keeping it in place is the pressure from the clutch fork, and the plastic strap while it's not installed.

Okay, appreciate the reassurance, I may try a zip tie on the boot to give it a bit more staying power. Rubber is not as spry as it once was. Was thinking I should just give it a go since I've got everything cleaned and primed with oil.

[War_Pony89]

After supper, put the  clutch knob unit into the cup, this time,  and had pressure on the clutch! Drove until warmed and shut off to retest. Started! so Think I nipped this issue of not starting after warmed. Thank you to y'all who chimed in before and recently.

[acfortier]

Well... Just got around to changing the CPS today with a Crown unit, and no luck. Won't even start this time. I'm at a loss here.

 

What else controls spark at the coil? Is there a way for me to test the CPS to know if it's good? Same with the coil?

[acfortier]

Heh, gotta love these types of problems.

 

Went to go check the resistance on the coil, and to confirm that the coil was getting voltage. 2 Ohms between the coil terminals, 10V at the plug when cranking. Seems like the coil should be fine... so I put the spark tester on the coil, and was getting spark. WTF.

 

Put everything back together, and it fired right up. Ugh. Not sure if that's a good thing or a bad thing?