help!!! xj wont start saga soap opera #2

[kirkandsylvia]

Ok...spent some time on my 96 xj today. Performed voltage test on crank shaft position sensor. With ignition on, found 5 volts going to cps on 1 of 3 leads...found middle lead ground reading in ohms to negative on battery...found 5 volts intermittent on 3 lead as I turned engine over by hand. That tells me that the cps is working. Now..checked voltage at coil via connector. On the green wire with orange stripe, I see 12 volts and on other wire in connector I see ground between it and negative on battery with ohm meter. So...i put the volt meter leads in the connector and with ignition on, I see 12 volts going to coil and as I turn engine over by hand, I do not see the voltage go to zero volts at all indicating that the engine computer is not breaking the negative to the coil and collapsing the field. I can hear the injectors clicking as I turn it over by hand indicating the computer is sending that signal, but not seeing voltage zero out at coil. I would think id see the voltage zero out shortly after I hear the injectors click as the pistons come up to tdc. Is there something im missing or does this sound like the computer is not breaking the ground to the coil to collapse the field. Bottom line....im not getting spark and its a new coil, cap, rotor, cam shaft position sensor, and crank shaft position sensor. I think I've done every test imaginable as far as electrical that would solve a no spark, no start issue. Any ideas? I'm thinking ecm is not doing what It should as far as the voltage to coil is concerned.

[Russ Chung]

Kirk,

WOW! It's been nearly three years since we last looked at it.
http://www.myjeeprocks.com/forums/sh...ht=#post224087
As I recall, there was a P0340 code (cam position sensor); we cleared the code and the AutoShutDown (ASD) relay was in the normal position. As soon as we tried to crank the engine, the code reappeared and the ASD went to the closed (shutdown) position. We changed the sensor, tried bypassing the ASD relay but there was no spark. As you noted in the above post, the computer is not sending the signal to the coil to create a spark. You also switched to another computer module that you purchased online but the results were the same. Are you are still getting the P0340 code?

Russ

[Russ Chung]

Kirk,

I think that the P0340 code and the cam position sensor (CMP) are giving us clues to where the problem lies. The computer (PCM) won't activate the coil when then CMP signal isn't present or when the timing of the signal is out of tolerance.

'When we last worked on the problem, we checked the wiring of the sensor circuits and they appeared to be OK. I don't remember if we checked the voltages that were coming from the CMP sensor. When the leading edge of the target wheel notch passes the CMP, the voltage should go to +5 volts, and when the trailing edge of the target wheel notch passes the CMP, the voltage goes to zero.
If the voltages are not OK, we would suspect a problem with the CMP sensor or the wiring.
If the voltages are OK, then the next thing to check is the timing/clocking of the target wheel. Rotate the engine until the timing mark is at top dead center (TDC); the alignment hole in the target wheel should line up with the mating hole in the housing. If it is 180 degrees out, then rotate the engine one more turn. If you cannot get the alignment hole to line up to line up with the mating hole in the housing, it is possible that the gears on the target wheel are one or more teeth out of position. Remove the assembly, rotate the gear one tooth, reinstall.

Russ

[kirkandsylvia]

I have read that the cmp can go out of tolerances which will cause start problems. I also read there is a way to realign it. Is this possible

[kirkandsylvia]

And yes...i do get the p0340 code. I'm thinking Napa tomorrow for new cmp sensor.

[Russ Chung]

I have read that the cmp can go out of tolerances which will cause start problems. I also read there is a way to realign it. Is this possible

1. Rotate the engine until the timing mark on the damper aligns with the top dead center (TDC) mark on the timing degree scale. If you remove the #1 spark plug, you can put a finger over the spark plug hole as you rotate the engine to make sure you are on the compression stroke and not on the exhaust stroke (unless you have VERY long arms, I think that you need an assistant to help with this).
2. Disconnect the CMP wiring harness and remove the oil pump drive assembly (OPDA) which houses the CMP sensor and the target wheel.
3. Remove the OPDA cover and temporarily install a small screwdriver through the target wheel access hole and then through the mating hole in the OPDA housing to prevent the target wheel from rotating.
4. Reinstall the OPDA housing into the engine while aligning the flat on the OPDA shaft with the slot in the engine. If the housing does not drop down flush to the engine block, then the shaft is not aligned with the slot.
5. Install the hold-down clamp.
6. Remove the small screwdriver, re-connect the wiring harness and re-install the OPDA cover.

[kirkandsylvia]

Ok..i think I'm alittle dumb here....is the opda the distributor housing?

[Russ Chung]

Kirk,

I found a better explanation of the XJ OPDA here
http://www.jeepforum.com/forum/f11/h...1145301?page=1

Russ

[kirkandsylvia]

Well...after 3 long yrs of not having my baby running, I have discovered the problem. And before I say what I found, thank you to all especially Russ for their help, opinions and suggestions. Most of you were all right in a sense as to the culprit, but what I never noticed in all the searching was the true gremlin. I decided today to look at the distributor and cmp one more time. With rotor cap off and cmp in hand, I noticed some plastic shavings matching the color of the stator plate under the cmo. After getting a closer look at the distributor I noticed I could see day light...yes day light coming from under the stator plate. I climbed myself under engine and looked up and to my surprise the motor mount was pulled completely from engine block and the bottom of distributor was sitting on top of the motor mount. This actually punctured the bottom of distributor housing allowing the mount to rub against the stator plate, which in turned, broke the stator plate from distributor shaft causing it not to spin while engine was cranking over. I never thought about it not spinning when I checked several times before to see if the rotor was spinning indicating the timing chain was still intact. There is my "no spark" issue. I can freely turn stator plate without turning the rotor...i guess you'd say "bad timing". What a great Easter present to myself to finally conquer this 3 yr soap opera saga.

[Russ Chung]

That's good news--I think. It explains the P0340 code and explains why the engine won't start. But fixing the broken motor mount sounds like you still have a lot of work to do.

[kirkandsylvia]

I think that wont be too bad. I've replaced drivers side motor mount before...it was a bit tricky lining up the hole for the pin...this is going to be alittle different. I have to first remove all 3 broken off bolts in the the engine block. After that...replacing distributor should be a snap. I'm still in a bit of shock that for 3 yrs I've have over looked what I should have seen. It just never dawned on me that just because the rotor spins...doesnt mean the stator was spinning. I just happen to catch it today...definitely explains a p0340 code

[6spdYJ]

Congratulations!

[kirkandsylvia]

Thank you. I've never had a mechanical issue take so long to resolve. And to think...i had a backhoe lined up and a perfect burial spot picked out in the corner of the property under a nice big oak tree