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morelia1976
July 7th, 2012, 11:47
Need some help. I have a 97 XJ 4.0 AW4 that won’t start. It stalled once while driving a couple weeks ago, and I thought it was due to low gas. I put some gas in it, and then drove to my uncle’s to do some planned maintenance. We did the brakes, changed the front and rear diff oil, put on an aftermarket rear bumper, and it drove alright for a couple days, then started stalling again, while at idle and driving. After a few searches, I checked the battery and CPS, both bad, so replaced them and the TPS. Went for a short test drive and continued to stall.
Checked new CPS, bad, took it back and got a new one. Tested this one before installing it, cleared the codes, drove about 20m and it stalled again. Backed it up into my parking spot, turned off, and tried to see if there were any codes. Wouldn’t display any codes, even though I’ve never had problems getting 12 and 55 to display on my odometer and wouldn’t start. Let it sit for a little while and it started. Turned it off, checked for codes and got 12 and 55. Checked the CPS and read ~5V across B and C with my ohmmeter, so it’s bad. Again. That was Tuesday. Since then it won’t start, just keeps cranking, and won’t display any codes. I also found out the fuel pump keeps going as long as the key is on, it doesn’t cut off after a few seconds.
I figure it’s a ground fault causing my troubles, but I suck at electrical. Any help or guidance would be greatly appreciated. I also plan on checking fuel pressure, but am more worried about the wiring.

GrimmJeeper
July 7th, 2012, 12:06
get a CPS from the dealer, all of the aftermarket ones suck.

morelia1976
July 7th, 2012, 12:12
Dealer is out of stock, told me Chrysler is on backorder, though I am looking at online sources.

morelia1976
July 8th, 2012, 17:21
So everyone else thinks its the aftermarket crank position sensor at fault?

Tim_MN
July 8th, 2012, 19:30
So everyone else thinks its the aftermarket crank position sensor at fault?

Cheap crappy "lifetime warranty" sensors ? No doubt. There are numerous threads that detail drive-ability issues that are cured with a genuine Jeep part, and faulty out of the box sensors from IdiotZone/PepBoys/Advance/O'Reilly's .

Genuine Jeep sensors are best, you can use NAPA sensors in a pinch.

morelia1976
July 9th, 2012, 11:34
Another new CPS ordered from www.mopar-wholesale.com (http://www.mopar-wholesale.com) will update when it's installed.

Would a bad CPS prevent any codes from being displayed?

gradon
July 9th, 2012, 15:47
Could be an ignition coil on it's way out too. Also, you "read 5V across B&C with your ohmmeter?"

morelia1976
July 9th, 2012, 17:29
I probably stated it the wrong way, but set multimeter to read resistance, put probes on the B and C terminals of the CPS and read about 5 volts (or ohms, or amps or whatever it's reading in). According to several sources, this is the proper testing method for a crankshaft position sensor. The reading should be for no connectivity. Thanks for the advice, I'll check the ignition coil as well.

Tim_MN
July 9th, 2012, 20:46
Would a bad CPS prevent any codes from being displayed?

yes.

CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)


http://fototime.com/78EA763821BA137/standard.jpg
.
http://fototime.com/269D7600706B48F/standard.jpg


TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

Flyfisher
July 10th, 2012, 21:14
and FYI...the fuel pump will continue to pump when the key is in the crank position. The short run is only when key is first turned to the run position.

morelia1976
July 11th, 2012, 15:05
Thanks for the info, the key is in the run position though. I'd turn key to run, then get out and put my ear next to the fuel tank. I don't really have anyone to help me on this, so there's no one else to crank it.

morelia1976
July 11th, 2012, 15:07
@ Tim_MN

Thanks for the info, and that is the testing method I used, though Haynes words it a little different.

morelia1976
July 16th, 2012, 19:41
Update: MOPAR CPS installed, jeep won't start. Tested CPS with multimeter set to 2000, read 1584 ohms, bad again. fml. No spark, pulled ignition coil (big PITA to get to those nuts on back of bracket) and it tests ok as far as I can tell (it doesn't match the pictures in the haynes manual or online guides. Online Chilton guide has no pics.) Distributor cap, rotor, spark plugs and wires were all replaced last March when the motor was replaced. Used shop towel and small bolt to test for fuel pressure (sorry I don't have a fuel pressure gauge) and got a strong stream of gas.

Any thoughts?

morelia1976
July 24th, 2012, 18:27
Solved: Got tired of banging my head over this, took it to my buddy's shop. Mechanic found a short in the ASD power supply wire that was messing with the CKP and CMP.

birchlakeXJ
July 24th, 2012, 19:01
ASD will shut you down every time if it's not up to snuff! Glad you got it resolved. Obviously your mechanic knew his way around the ASD system.
-----------------------------------------------------------------
Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark.

morelia1976
July 25th, 2012, 21:26
Yeah, it only took him about 3 hours. It would've taken me 3 months of procrastinating and half-***ed searching to find it. I hate electric problems, but there's no escaping them without driving something pre-1970.

Shoeman
July 28th, 2012, 05:25
Umm..whats ASD stand for? I'm having similar issues. Thanks for the CPS test info!

RockyMountainXJ
September 5th, 2012, 20:38
will the ASD keep it from getting spark?

comanchechuck
September 9th, 2012, 17:29
I have the same issue on my 99 xj. Where exactly did he find the short in the system. Would really appreciate some feed back. Thank you very much.

Faz95XJ
September 20th, 2012, 17:06
Follow on question to the replacement of the CPS....

I was at the VA 4WD annual run last weekend and had a few instances of "no spark" which were believed to be the result of a unhappy CPS. Consensus was that the CPS was getting too hot. Once the engine cooled, it woudl restart.

Folks on the trail said I would need a "Sh!T-pile of extensions to replpace the CPS, but the pictures I've seen don't look like connections that need a socket or anything like that.

Can someone clear this up for me?

birchlakeXJ
September 20th, 2012, 17:09
Folks on the trail said I would need a "Sh!T-pile of extensions to replpace the CPS, but the pictures I've seen don't look like connections that need a socket or anything like that.Can someone clear this up for me?

Here is a good thread that details what needs to be done to change your crank sensor. Good luck and hope you have small hands!

http://www.go.jeep-xj.info/HowtoCPSchange.htm

Faz95XJ
September 21st, 2012, 10:12
Thanks.

That does not look like fun.