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Discussion Starter · #41 ·
This may sound nuts...........lol
Next time it starts acting up, pull both alternater fuses....and see if it suddenly works perfect. dont drive to far.....no alt.
I had the same issue.....changed all kinda parts to no avail.
My alt showed it was charging just fine, BUT it turns out the field was going bad, just alittle, and it was causing my ecu to have fits.
Stalling.....sputtering....back fires, as if ignition was failing. I bashed my head on it for days.
I pulled my alt furse, drove like a charm, so new alt, fuses back in.....perfect.
Alt will show charging fine on a tester too.....thats why you must pull fuses to see if prob goes away
Does that method work for an 89 3-wire alternator or is it for a 94 4-wire
 

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Does that method work for an 89 3-wire alternator or is it for a 94 4-wire
You don't have fuses for the output you have a fusible link. It's different.
 

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Discussion Starter · #43 ·
So it looks like I may have finally fixed the issue, I just drove a 2,000 mile round trip across states with no problems anymore

It was caused by the crank sensor not being set the right distance away from the pulley, as far as I know. It's also winter time so the engine wasn't running hotter
I replaced the crank sensor (again) and this time I set the clearance to 0.001" instead of the 0.040" that is usually recommended using one of the tabs off the box the sensor comes in. Didn't have any issues with it on the whole drive.
 

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So it looks like I may have finally fixed the issue, I just drove a 2,000 mile round trip across states with no problems anymore

It was caused by the crank sensor not being set the right distance away from the pulley, as far as I know. It's also winter time so the engine wasn't running hotter
I replaced the crank sensor (again) and this time I set the clearance to 0.001" instead of the 0.040" that is usually recommended using one of the tabs off the box the sensor comes in. Didn't have any issues with it on the whole drive.
Thanks for posting the fix. You're the second one in a few months that have replaced the CPS and had issues with the distance.
 

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Discussion Starter · #45 ·
So it looks like I may have finally fixed the issue, I just drove a 2,000 mile round trip across states with no problems anymore

It was caused by the crank sensor not being set the right distance away from the pulley, as far as I know. It's also winter time so the engine wasn't running hotter
I replaced the crank sensor (again) and this time I set the clearance to 0.001" instead of the 0.040" that is usually recommended using one of the tabs off the box the sensor comes in. Didn't have any issues with it on the whole drive.
Thanks for posting the fix. You're the second one in a few months that have replaced the CPS and had issues with the distance.
Yeah I've seen a few times how people had issues with their sensor distance and I always set it using the tab off the box

Since the sensor is just a magnet the distance away has a big effect on how strong of a signal it can read
 

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did you know....if Que calls your house....your jeep will start and run JUST out of respect?
true story.....worked for me
It's a Zen thing. LOL
 

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Nah I'm good I turned around and took it home then took my other car down to Dallas. Still annoying though. Back to square 1 I guess

I changed out the MAP sensor this time but I can't really test if it fixed it or not because I have to drive long distances in hot weather.
Let me know when you're back to troubleshoot it.
 

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Discussion Starter · #52 ·
I'm not sure where to start this time. I think the computer might be overheating since it has a layer of dirt on the inside so might try that next

current project is putting the head back on because somehow I popped off the freeze plug on the back of the head while going down the highway and it dumped all the coolant in 10 seconds
 

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I'm not sure where to start this time. I think the computer might be overheating since it has a layer of dirt on the inside so might try that next

current project is putting the head back on because somehow I popped off the freeze plug on the back of the head while going down the highway and it dumped all the coolant in 10 seconds
Let me know when you're ready.
 

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Discussion Starter · #54 ·
So here it is approaching summer time and it happened AGAIN even after I thought I fixed it (tracing it to I think the fuel rail is vapor locking because my engine runs hot)

I bought one of those fiberglass fuel rail insulator kits and thought that would fix the issue but it did it again on my ride back from an offroading trip

Once again, it started up after sitting for 20 minutes and I drove the rest of the way home.

Well, this Sunday I took it out and parked it at the store, then it wouldn't start back up in the same manner that it was doing when driving on the highway. When turning the key I noticed I wasn't hearing the fuel pump turn on anymore...so... I guess this 3 -year problem finally comes to a close with the death of my fuel pump.

Except today I jumped the fuel pump to +12v and it kicked on, so after some wire testing I found that the relay wasn't getting power. So at this point I decided to unplug the PCM socket and then plug it back in, and surprise surprise - it started working again.

It looks like the PCM was never plugged in all the way so the connections filled with dirt and sand over time. I am going to the store to get terminal cleaner and dielectric grease and I hope this was the issue the whole time and it's not something else.
 

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Thanks for posting your fix. Alot of people get it fixed and dissapear and we never know what the actual fix was. I bet within a few years you will have saved alot of people the frustration you just went through just by posting your fix.
 

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Discussion Starter · #56 ·
it did it again last weekend. What a joke, this is getting ridiculous

I had friends with me this time and I had them try to start it, the fuel pump kicks on when cranking so it's definitely NOT that now, and that means the crank sensor is also working correctly

I feel like this is just a complicated case of vapor lock at this point. 130 miles one way, it did fine this morning with the engine temp constant at 195. On the way home the temp was floating around 200-220 and it died about 70 miles into the drive.

I have the DEI fiberglass heat wrap kit for the fuel rail. I currently have a 195 thermostat in it, which was a recent addition when I switched to the electric engine fan. It originally had a 180 thermostat and mechanical fan with a stuck clutch so the temp was never above 180 (and subsequently this problem never happened)
 

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it did it again last weekend. What a joke, this is getting ridiculous

I had friends with me this time and I had them try to start it, the fuel pump kicks on when cranking so it's definitely NOT that now, and that means the crank sensor is also working correctly

I feel like this is just a complicated case of vapor lock at this point. 130 miles one way, it did fine this morning with the engine temp constant at 195. On the way home the temp was floating around 200-220 and it died about 70 miles into the drive.

I have the DEI fiberglass heat wrap kit for the fuel rail. I currently have a 195 thermostat in it, which was a recent addition when I switched to the electric engine fan. It originally had a 180 thermostat and mechanical fan with a stuck clutch so the temp was never above 180 (and subsequently this problem never happened)
Vapor lock shouldnt be an issue sonce your running 30+ psi at the rail. I havent read back through the whole thread but have you replaced your fuel pump. I had one do this when it would over heat. Never did it on a full tank and only did it on HOT days like over 95 degrees. But it got to the point if it was over 95 degrees and I drove for an hour or more once I got to a half tank it would start acting up. Give it 20ish mins and then it was fine for another hour.
 

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Discussion Starter · #58 ·
The pump is only 4 years old, it's an inline pump I installed in 2015, as well as an inline fuel filter before it. I changed the fuel filter a few months ago because I thought that was the culprit
 

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The pump is only 4 years old, it's an inline pump I installed in 2015, as well as an inline fuel filter before it. I changed the fuel filter a few months ago because I thought that was the culprit
I have had 2 pumps go out in under a month. SO going bad in 4 years is not unheard of. There is an easy way to find out. THrow a fuel pressure gauge on there when it does it again. It will also tell you if its vaporlock since if you hit the button if you ddont get liquid fuel its vapor locked. You can get a gauge off amazon to keep in your jeep for like $20. Just a thought. Your issue definitly seems heat related. I also had an alternator that when it got hot and only at RPM the field coil would short and basically take the ground from everything so it made the jeep buck like a horse because it would short kill groud everything shut down then the dhort dissapeared everything powered up it would do this over and overt and over really fast. Give it 20 minutes to cool down and it would be fine again for a few minutes. I have also heard of Crank position sensors cutting out if they get hot enough then when they cool down they work again. ANother thing you can do to check vapr lock is keep a can of canned air for cleaning compputers when it does it. Turn the can upside down so the liquid comes out and spray the rail it will cool it down quick. I have seen this done with crank and cam sensors too.
 

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Discussion Starter · #60 ·
Is there a way to test if it's the alternator? the symptoms are similar, it definitely backfires like the ignition shorted out

the alternator is the original one with 177k, and is not wired up to the engine computer since it's from an 89 and not a 94.
 
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