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Discussion Starter · #1 ·
Running down the road yesterday and the tj went to spitting and spuddering. It sounded like it had jumped time and I was actually convinced it was an ignition problem. Checked the coil wire, all connections, looked over everything, but after about 10 min found no loose connections or evident problems. I tried to start it angain and vroom started like normal. With just under 1/2 tank of fuel i was convinced it was a ignition problem. 97's don't have the schrader valve in the rail so I only know that it is getting fuel cause it fires.

Knowing coils degrade and have caused similar symptoms in the past, after the calvary arriver, Thanks Tim Aaron and Austin, we changed the coil. Jeep fired up and ran like a champ. I thought it was heat related so we let it sit and run for about 30 min when we returned she was Idling like a champ. Rolled it off the trailer and drove about 6 blocks and same thing happened acted like it jumped time. Still believing it was getting fuel and not smelling rich We put a crankcase position sensor in and again fired up and ran but for less time. Didn't even get out of the parking lot.

So that is where I am with 150 in parts and no progress.

Any Ideas?
 

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not quite the same symptoms as when my fuel pump on the ZJ went out, but when it's doing this and it shuts off, can you crank it right back up? Or does it continue to not run? if it doesn't run, pull the fuel return line, attach a hose to it and point it in a bucket, and have someone turn it over. This will give you an idea or fuel supply. Yes I said supply. the supply is more than the engine can use so it returns quite a bit.

When my pump went bad, Caver and I did this to empty the tank and got nothing from the return. as a "test" after we replced the pump, we did this exercise again, and it pump a good volume back thru the return. Not a be all end all test, but coulc give you an idea on if your pump is supplying enough.
 

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The first thing I would do is check for trouble codes, if there were no trouble codes I would test fuel pressure, If that looked good I would suspect the other cps, the Camshaft position sensor. (even if it had not set a code)
 

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That sounds like the typical CPS trouble.
Start by finding the connector, unplugging it, and plugging it back in again. Some of them are factory mounted with a strain on the wire - that may be the reason they fail, not sure.

The CPS is located in a terrible place - on the bellhousing's top, slightly to the left side. You can see it from underneath.
The connector is top left side, near the Master cylinder. You can see the 3 wire plastic connector and the small harness running down behind the engine.
For some reason, those connectors must get corroded inside, the act of dissconnecting/connecting sometimes helps.

The older CPS is about $40 I think, later model ones are more like $140.
 

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[ QUOTE ]
put a crankcase position sensor in and again fired up and ran but for less time. Didn't even get out of the parking lot.

So that is where I am with 150 in parts and no progress.

[/ QUOTE ]

Pretty sure he meant Crankshaft Position Sensor but I could be wrong.
 

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Sounds real similar to the problems I'm having with a 2.5L. Be sure and post what finally fixes this.
 

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I had a similar problem with a Ford it turned out to be a vacuum line with a crack. It would idle all day but when I drove it, it would act like it was fuel starved. And would not trip any codes. If I remember right it was the line that went to the EGR. Good luck
 

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He He - If the crankcase is upside down it would look strange!

Sorry, typo - Crankshaft Position Sensor! AKA CPS (Not Child Protection Services either.)
 

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Try a new distributor rotor. Had a real strange one a few years ago that would cause engine to stall sometimes. Looked for months until the rotor finally gave out... Tow truck, a few hours of shop charge. $2.00 rotor. Apparently it had a pin hole through the base and there was loose plastic in the hole, under the right rpm, and bounce it would dislodge the loose plastic and shut down the engine.
 

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It wasn't your typo. Man what you been smokin this morning? Can you send me some? /ubbthreads/images/graemlins/grin.gif

Since the CPS has already been changed, unless there was a code pointing to something else, I'd highly suspect the camshaft position sensor (CMP). I've seen more than one CPS be faulty without setting codes, being the same type (Hall effect) sensor I assume the CMP sensor could do the same.
 

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The camshaft position sensor sends the computer the pulse that tells the computer which injector to fire. This usually does not cause a backfire problem, and normally DOES set a code.
 

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According to the FSM,
[ QUOTE ]
Its signal is used in conjunction
with the crankshaft position sensor to differentiate
between fuel injection and spark events. It is also
used to synchronize the fuel injectors with their
respective cylinders.

[/ QUOTE ]

I don't doubt it usually sets a code. And may have done so, he hasn't said yet. I read the above passage to mean a malfunctioning CMP could cause problems similar to a malfunctioning CPS but I'm just guessing. What I would do if it were mine would be to borrow parts fom a friend for trouble shooting (if there were no codes), but not everyone can do that, it's one of the advantages of belonging to a good off road club.
 

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Discussion Starter · #13 ·
Sorry for the delay and lack of compleete explanation in the beginning.

in fact there are no codes. In adendum to the above we also put a new coil wire on it. The old one broke during coil install.

I ordered a camshaft sensor to try tomorow. No that I am home I can play the see if this works and if it dosen't they take it back.

I talked to a dealership guy today and he said he bet on the camshaft position sensor but recomended that I toss on a new cap and rotor at the same time.

I drove to Bloomfield and got it today. like 6 hours of driving in a truck that wasn't comfortable when it was manufactured. It started right up and pulled onto the trailer. It ran until I shut it off, but did mis a few times while idling.
 

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Just had the same thing happen to a buddies 2.5L pulled the distibutor and the gear was about gone causing it to get out of timing, but that was with about 150,000 miles on it.

Brad
 

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"""""It wasn't your typo. Man what you been smokin this morning? Can you send me some? """""

He He - I guess it was working! He said he'd already replaced the crankCASE position sensor in the first thread. I was thing he meant crankshaft, but typed out crankcase. Not only did I miss what he meant, I continued the error.

Gotta get some more of that stuff!
 

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I've said it so many times before - but I'll bet this isn't the last.

Back to basics.
Compression - (you can hear if it's jumped a chain.)
Fuel - Shoot a bit of propane to it - if it's a lack of fuel, no matter what the injectors do, or don't do, it'll run.
Spark at the right time - Put a timing light on it - check the timing while cranking. Look for wrong timing, no spark, random sparks etc.

No matter how complicated the computer system is, it still needs the above! First you need to know what area is failing before throwing parts at it.

Codes often have to have the malfunction happening for several minutes before they set. Often when something fails, it's immediate - too fast for a code.
 

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[ QUOTE ]
in fact there are no codes.

[/ QUOTE ]

My son just recently had his 00 Cherokee have a no start condition. I have an OBDII scanner and the internal diagnostic via the odometer display.. Both produced NO CODES. It ended up being a crank sensor.

It's extremely difficult to check for spark on an 00 due to the 3 jugs being semi integrated in the "rail".

Go figure /ubbthreads/images/graemlins/confused.gif
 

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Discussion Starter · #18 ·
Rrich I know you are right. The problem I am running into is that the problem is intermitant and I can't get it to do it on command. When it does I cannot get it to do anything.

Today I drove it around town here to there never shutting it off, after about 3 hours I decided it was gonna be ok, I took it out to where I am junking some cars and left it run for another hour while I winched cars over to cut out tanks and back on their wheels. On the way home no missing or anything. I pulled up to the light in town and bam it spit and backfired hard through the carb and stopped.

It took about 20 minutes to get it to start. Couldn't get it home so I picked it up with the trailer. Got it home pulled out the light, propane and tools only to find that it fired up and ran without incident for another hour.

So I am ready to do the diagnosis but I can't make it do it on command.


Besides it is imobile right now because I cut A tire pulling it off the trailer.
 

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How 'bout taking the propane with you?

You could even put the bottle and valve on the front seat and run a hose up to the air cleaner.
 

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So Rio, did you ever get your Jeep fixed? I hate it when a story just fades into oblivion without a happy ending!
 
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