REALLY stumped could use ANY Help/Guesses

I have a 96 Cherokee Sport 4x4

I have had the fuel sending unit replaced (my year Jeep was the cross over year and mine has the fuel pump/regulator in the tank, a ONE YEAR only item --looks like this http://www.cherokeeforum.com/attach...fuel-pump-sending-unit-96fuelpumpassembly.jpg), the fuel filter replaced, oil pressure switch, crankshaft position sensor replaced, the water pump & thermostat are new, as well as the spark plugs & the battery, starter, ignition switch as well as alternator.

Heres my perplexing issue:

While driving down the road my 1996 Jeep Cherokee Sport 4x4 (4.0) just straight dies, no coughing, sputtering, nothing. It just dies. It wouldn't start back up....cranks like it wants to start but just doesn't. There are no lights on, on my instrument panel other than low windshield washer fluid because I always forget to refill that! lol

After killing the battery trying to start it I'll recharge the battery, on the battery charger by letting it sit over night, it'll start back up the following day once the battery is charged.... I can drive it anywhere from 20 minutes to a few hours, then BAM it just dies. I have to say it drives like a work horse, and you'd be as stumped as I am that it just dies, sometimes while slowing down to stop, sometimes while zooming down the road at 50mph.


Please if you've experience this yourself and could share what YOUR issue was, that would at least be a start because honestly I just haven't a clue what on earth is causing this.:idea:

Thanks!

Check the voltage across the battery terminals with the engine running..it should be around 13.5- 14.2 volts..Just because the alternator is new doesnt mean it's good...I had a buddy who got 3, yes, 3 bad ones in row from Pep Boys.

When my XJ did that I would simply ignore it (not try to start it for 20 to 30 minutes then it would start right back up and run like it did not even happen. If I try to start it right after it quit it would appear as if it will start but would not. The perplexing part of the whole thing was, it would start cold and run perfect 20 to 30 minutes. When the engine is hot, the run time would get progressively shorter.

It turned out to be the O2 sensor. The generic error codes would make it appear as if every engine control sensor was bad, all except the O2 sensor for which there was never a code pointing to it. The funny thing was, that sensor was recently replaced (maybe 2 months earlier) to remedy a high fuel consumption and the previous one also did not send an error code. That was an Auto Zone version of the Bosh brand.

This may not be your problem but it is worth looking at.

Thanks for both of those suggestions, I definitely checked the voltage with my multi-meter and the voltage is fine, as for the O2 sensor, I thought of that but wasn't sure if that was a possibility of being the issue.... I'll take note of that for sure, as a possible fix though... if it fixed your issue, it may possibly be mine as well.

First step is to verify the likely condition of "no spark" when it won't run. Pull a plug wire and hook it to a extra spark plug. Ground it to the block or head and check for spark with a helper cranking. Let us know the results.

where did you get your new crank position sensor from? if its not from the dealer, and from a parts store they are hit or miss with issues right out of the box. if you can find a known working sensor try using that.

I agree with the parts store cps. I got lucky with the second one.

OEM Sensors x3 (if you can't get OEM, NAPA is your best alternative IMHO).

I've also had an O2 sensor kill my wrangler while getting off an offramp. Turned out when I installed the header I routed the wire wrong and it melted while driving.

While I highly doubt it's your issue, it is proof a bad O2 will stop your engine even at highway speed. 5-90 has a write up on checking your O2 sensor, do a search for it and try that.

Another possibility might be the CMP/Cam Position
Sensor. It's located directly under the distributor
cap and is held in place by the two dist cap screws.

My 96's CMP has failed twice now, and left me
stranded on the side of the road once. Check
the sensor magnet to see if it's still glued in place.

Sounds like a bunk crank sensor to me

Okay....Thanks for ALL your suggestions and help. I greatly appreciate it.

My parts, I always buy oem parts from the dealership as it's right down the road to me and closer than Autozone/Advance Auto is, and I was told some time ago on here it's usually best to stick with OEM parts so I do.

I have tested the spark issue and theres no issue with that....

I have no idea What you meant by 5-90's write up on how to check the O2 sensor, explain if you would, I'd like to check that!

I honestly don't think it's the Crankshaft Position Sensor, seeing that it was replaced less than 2 months ago, but I agree that at times, we can get bad, new parts, so I am now left to ask, as I was told by a friend who is as stumped as I am... Would the CAMSHAFT Position sensor do this? Is this actually something that you've had to deal with and replacing it, fixed the issue?

Thanks~!

EDIT... I've located 5-90 and I am searching his posts for information on testing the O2 sensor, so far have not located that thread yet.

I've had that happen to my 96 a few times for different reasons. First time it was my CPS, though mine didn't seem to be temperature related, it was pretty random, happened cold and hot. The odd part was the CPS tested good by the book, but it had a short in the the other non test poles which wouldn't show up with the book test. The first thing I noticed when I tried to get the key codes (MIL codes) was my check engine light was dead, it wouldn't light up when I turned to the key to run. I don't know exactly what the connection was between the CPS and the check engine light, but when I unplugged the CPS the check engine light came back on and I could retrieve the codes. I never did get a bad CPS code though. I did measure my CPS supply voltage (with the CPS connected) and it was three volts, which lead me to believe the partial short in the CPS was sucking down the sensor supply voltage. The Sync sensor and the CPS share the same sensor voltage supply source, at least in my early 96 model, the late 96 models may be different in this aspect. Best guess is a shorted sync sensor can also mess with your CPS supply voltage, though I've never had *that* issue.

Second time my CPS was covered in grit and partially dried oil form a leaky valve cover gasket. The CPS started acting up. I cleaned off the CPS (with brake cleaner) and it has been working fine since. Best guess is the grit and oil collected some metal filings and was messing with the CPS. I actual bought a new CPS (which is now a spare), but never needed it after cleaning the old one (it's been in there years). The only reason I sprayed it down with brake cleaner was to clean off the old CPS and the surrounding area, to replace the CPS and decided to try for a start one last time (on a hunch) which saved me some unnecessary wrenching.

Third time my dealer installed anti theft module was acting up and cutting off power to my ASD relay. I unplugged it and jumped all the wiring after I found out the company that manufactured it went out of business and replacement modules weren't available.

Yours seems to be temperature related, a trick I've used on my Renix that may work on the 96 also, is when the motor dies (while hot) pour a quart of water onto the CPS to cool it down and see what happens. Worked on my Renix, may also work on an OBD model. If you pour a quart of water on the CPS and the motor starts, it almost has to be the CPS. A low tech test that may help you nail down the problem.

I also had something similar happen twice, the first times when my alternator was dying and a year later when my battery was dying. Sporadically, when I'd let my foot off the gas pedal, the motor would stall out from lack of air. The IAC would stick shut. The first time with the alternator it was mostly when the motor was cold, the second time with the battery it was mostly when the motor was hot (but the weather was cold) and after multiple stops and starts.

One thing you always want to look at is the wires running from the connector to the CPS. If they aren't tied down out of the way they can flop onto the exhaust manifold a cook there. This can either kill the motor altogether or it may be a sporadic event,

doostica said:

Okay....Thanks for ALL your suggestions and help. I greatly appreciate it.

My parts, I always buy oem parts from the dealership as it's right down the road to me and closer than Autozone/Advance Auto is, and I was told some time ago on here it's usually best to stick with OEM parts so I do.

I have tested the spark issue and theres no issue with that....

I have no idea What you meant by 5-90's write up on how to check the O2 sensor, explain if you would, I'd like to check that!

I honestly don't think it's the Crankshaft Position Sensor, seeing that it was replaced less than 2 months ago, but I agree that at times, we can get bad, new parts, so I am now left to ask, as I was told by a friend who is as stumped as I am... Would the CAMSHAFT Position sensor do this? Is this actually something that you've had to deal with and replacing it, fixed the issue?

Thanks~!

Click to expand...

"No issue with spark". Does that mean you do have a good spark?

Hello Winter Beater, yes I have NO issues getting spark. I have new plugs as well, although they weren't needed, I put some new ones in anyways....

I am still stumped and perplexed on what on earth the issue could possible be.

I wish I could give more details but what i've stated is pretty much all the details I can provide.

An old school troubleshooting trick if you think you have spark is to spray come carb cleaner down the throttle body while cranking. If it fires for a moment, it is a fuel delivery problem.

If it is a fuel delivery problem and you have checked fuel pressure at the rail, you most likely have an injector drive problem. To have a total no fire situation, it has to be something common to all injectors. That most likely rules out wiring back to the ECU. Have you checked all the fuses? I'm not familiar with what year you have, but many vehicles have a fuse for the injectors that is separate from all the other wiring. Also check for an ECU fuse.

As all of the others have already said, when the no run/start condition presents YOU must identify the MISSING ELEMENT.

You say you have spark, then check with a NOID light and see if you are getting an injection pulse. If you are getting the injections pulse, then check your fuel pressure and volume.

Post up what you find, or don't find.

I can't believe I didn't update this and fill in what the cause was:

I replaced the distributor, the sensor above it, the cap & rotor as well as my Crankshaft Position sensor and my Throttle Position Sensor (altogether it wasn't all that much, I figured hey preventative maintenance if none of these are necessary) and that fixed my issue.