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Attempts to start but won't stay running - '96 XJ


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First off, I want to say sorry if this is in the wrong section.  Admins, please feel free to move if necessary.  Also, I realize this is an MJ forum, but y'all are considerably more helpful than the other forums I'm on.

 

Ok, so here's the issue...

 

I've been working on my buddy's '96 XJ - 4.0L, AW4, ~280,000 miles, pretty much stock.  It has been unhooked to a battery in quite some time due to the slow progress I've been making in performing repairs between my main job.  It won't stay running after it attempts to start.  So far, I've done various fixes to try and remedy this, such as:

 

- New distributor cap, rotor (brass terminals), spark plugs and wires

- New timing chain and sprockets (installed just like my Haynes and Chilton manuals specify)

- Checked and indexed the distributor just like cruiser54 instructs and verified wires are in 1-5-3-6-2-4 order

- Used a known good, charged battery

 

I know that there has been a similar issues with the OBD II models where to floor it to get it to start it after the battery has been disconnected since the computer has to "relearn" idle settings, but this is not the issue here as I've experienced that on this same Jeep a couple years ago.  Also, something to note, more often that not, when you attempt to start it, it sounds like the starter and flywheel are binding (not a grinding sound, see the video below - it can clearly be heard after the 3rd attempt to start the engine). It's done that since the Jeep was purchased but seems like the computer compensated for it after a while, which suggested a timing issue to me, thus the whole reason I checked and replaced the timing chain and distributor.

 

I'm stumped, so... smiley-sign0085.gif?!

 

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That binding sounds like the timing is off to me . I understand you checked and replaced timing chain etc .Have a friend turn the distributor slightly each way while you're trying to start it to see if you can get it to run .

Timing is off

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Agree, I think it's timing caused by the distributor being indexed a tooth off. Pull the dizzy until it disengages and turn the rotor one tooth clockwise and reseat. If no joy, pull it again and turn the rotor back two teeth ccw and reseat. Also check for a worn dizzy drive gear and pinched wires on the sync sensor. .

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Thanks for the helpful replies.  I actually have done exactly what Stroker suggested with slightly advancing/retarding the timing by turning the dizzy.  However, that proved to be useless.  That being said, I've also pulled said dizzy and redropped it back in a few times in my attempts to remedy this.  I've set quite a few dizzy's in the 4.0 previous and been successful.  Not saying that I couldn't be off this time, it's always possible.  What's crazy, and perhaps I should've mentioned it in the original post, but that "binding" has been a problem since the Jeep was purchased from the original owner, but as it would seem, the problem was rectified by the PCM somehow since it was starting and running before the battery was disconnected.  Also, perhaps worth mentioning, if you ever got heavy on the accelerator or put the engine under heavy stress (like we did pulling a compact car 5+ hours a couple years ago), the engine ran like crap.  Sounded nearly identical to how it would sound if the vacuum line to the MAP sensor was disconnected.  Funny thing is about that, that issue would go away after the engine cooled overnight and be fine by the next morning.  Not sure if that's related.

 

What I will do, is go over might work with the distributor and verify it is set correctly.  Afterward, I will report back.  Thanks again for all of your suggestions!

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*UPDATE*

 

So, I re-dropped the distributor.  Seems I was off, as suggested.  I have it installed and the rotor is aligned just as my other XJ is.  The trailing edge of the rotor contact is just past the first post.  It starts and it'll idle ...mostly.  Problem starts at ~1400-1500 rpm... It begins to spit and sputter, backfire and pop like there's no tomorrow.  Now that it "runs", it finally threw the CEL on and I was able to pull some DTC's.  I did the old key/ignition trick and used a scanner.

 

Key trick showed codes:

  • 12 - Battery/PCM disconnected within last 50 starts
  • 27 - Fuel injector circuit open or not working (this code threw twice)
  • 54 - Distributor sync sensor fault

OBD II scanner showed codes:

  • P0340 - Camshaft Postion Sensor Circuit A error
  • P0205 - Fuel injector #5 circuit open or shorted
  • P0206 - Fuel injector #6 circuit open or shorted

I swapped the distributor pickup coil with another one and it made no difference in how it ran.

 

It has the Neon 703 four hole injectors in it and was running fine before, so not sure if those codes are relevant.

 

I've been told that if the P0340 code is thrown, it could also indicate a problem with the crankshaft sensor.  Assuming that was even the case, wouldn't the Jeep not even run or start?

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Got a timing light? It would be good to see if your timing is advancing with the RPMs. Stick it on #1 plug wire and look at the timing marks on the timing chain cover at about 1200 RPM. It'll jump around a bit, but the light should be fairly steady @ 14* - 18* BTDC and advance slightly as you increase RPMs. You can't adjust timing, but at least you can see if the advance signal from the ECU is proper.

 

I don't know if the key trick codes are valid on a 96 since it's a bastard OBD2 system.  :dunno:

 

 

When you say "swapped the distributor pickup coil with another one", are you saying you swapped the sync sensor assembly? Does your distributor look like the below?

 

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Got a timing light? It would be good to see if your timing is advancing with the RPMs. Stick it on #1 plug wire and look at the timing marks on the timing chain cover at about 1200 RPM. It'll jump around a bit, but the light should be fairly steady @ 14* - 18* BTDC and advance slightly as you increase RPMs. You can't adjust timing, but at least you can see if the advance signal from the ECU is proper.

 

I don't know if the key trick codes are valid on a 96 since it's a bastard OBD2 system.  :dunno:

 

 

When you say "swapped the distributor pickup coil with another one", are you saying you swapped the sync sensor assembly? Does your distributor look like the below?

 

 

Yes, this is the exact style dizzy and pickup/sync sensor it has.

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Got a timing light? It would be good to see if your timing is advancing with the RPMs. Stick it on #1 plug wire and look at the timing marks on the timing chain cover at about 1200 RPM. It'll jump around a bit, but the light should be fairly steady @ 14* - 18* BTDC and advance slightly as you increase RPMs. You can't adjust timing, but at least you can see if the advance signal from the ECU is proper.

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  • 4 months later...

Alright, finally got back around to messing with this thing.  I recently acquired a spare 4.0 from a '97 XJ and I swapped the distributor from it into my buddy's.  Fires right up, with no hesitation and revs up just like it should.  So it was the timing, but nothing that I was doing wrong.  Hate when things make you second guess yourself lol.

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Bad sync sensor........

I swapped it months ago with a working good one and it made no difference.  It was the distributor itself.  The rotor wasn't pointing where it was suppose to no matter what I did (and I've set a many distributors in these things).  I swapped one in and it was right on the first attempt.  Fired up and it's running well now.

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