Bullstang360

So this started as a different thread but evolved into something bigger and figured I should start a new thread with the new info for better results. So last Friday I was headed to work and as soon as I pulled out of my driveway my Jeep just died with no warning. So far I have checked all my fuses and swapped around relays to rule that out. I also cleaned up all the ground connections I could find. Then I replaced my CPS and still had no start. I checked for fuel (not with a pressure gauge, just with the check valve) and it is there and even tried starting fluid just to be sure. So now I started to look for spark and found none. I checked my spark plugs and they seemed a little bit warn for their age. So I replaced all my plugs, wires, cap, rotor, distributor, and coil but, still had no spark. I even tested with an inline test light. So I was hooking up my battery charger and noticed a small ground I missed and when I was cleaning it up my ear was next to the ECM and I could hear a faint high pitched noise comming from the ECM so I double checked that the key was in the off position and found that it was still in my pocket. So now im thinking the ECM might be to blame. I went back to the connector for the CPS and tested the connector on the harness side with the key in the on position and found zero volts on one pin, 5v on the next pin and 9v on the last pin. This doesn't seem right to me, so im wondering it this is a sign the ECM is bad? Is there an easy way to test the ECM? I'm about burnt out on this and almost ready to take it to a mechanic but figure I would try mt luck here one last time. Any help is apreciated.

Radi

Every time I've heard a PCM/ECU start squealing it's had a failing power supply regulator. I'm not sure how you could test it other than substitution.

DFlintstone

RRRRR. I just lost a couple paragraphs of text again. I'd rather hit my finger with a hammer! (So here is the angry version)

Arrrr!!! 9 vol;ts doesent sound right since it only gets 5 from the RRRRR PCM. (Powertrain control Module) ECU in 90 and eirlier. You might find this helpru;; http://www.cherokeetech.com/VBull/sh...agnosis-Videos

See if you can find a code reader and/ or try the " key trick . Your OBDI (on board diagnostics) stores error codes. (they are listed at the top of the forum

. The "Key Tricks"
Older (OBDI) models - Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. ("On" is NOT "Start" and "Off" is NOT "Lock"). The "check engine" light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

You might check the wires grounding at the dipstick stud. 87-90 everything grounds there puter, tcu everything....

Bullstang360

Yah thoes grounds were the first ones I checked. My other thread that led to this one was actually on my check engine light not working. I tried several times and couldn't get the key trick to work using a test lamp

DFlintstone

You sure got me. I might see if the PCM still makes noise with the CPS unplugged. (just for lack of a better idea)....9 volts at the CPS and noise from the puter sure sounds messed up. I wonder if it's drawing extra current or getting warm. I wonder if you can rent a code reader/scanner from somewhere like Auto Zone.....

Hopefully someone more familiar with OBDI will chime in.

Bullstang360

I called around they only rend odb2 readers and i have one so looks like ill be buying a combo obd1 & 2 reader this time couldnt hurt to have on hand i guess. I seemed strang that on the harness side on the CPS I had 5v on one terminal and 9v on the 3rd one. Is it dual fed?

DFlintstone

I thought that might be in the link I posted in post #3?

Bullstang360

Good videos was at work just had a chance to watch them.

Bullstang360

So those videos are awesome. I started doing a lot of close looking around I checked the wiring harness and it all lookes good without removing the loom completely. I started digging around and that 9v on the CPS sensor connector on the harness side was really bugging me. I checked the ground at the connector with a continuity tester and its good to the battery and to a few other grounds around just to be sure. The other socket on the connector is my 5v reference which was good. So now I come to the last socket on the connector which is the one that I read 9v on. This should be the return signal from the CPS sensor so the only voltage on it should be coming from the sensor not the computer. So I now believe that I either have a line to line short some where in the harness or something in the harness is shorted out. Anyone have any input or know where I can get a good wiring diagram online. Found a few just a little lacking in detail.

DFlintstone

Howdy! I tried to view that video myself but my connection/security made it mess up. Anyone else on "slow", I think the second one down is CPS, (the first is the cam sensor. Btw 89laredo I think, is who had that.

A side story. I had an aux battery on an isolator. (in the trunk of my 72 Celia). One day I looked out a second story window and saw my wipers going and smoke coming out around my hood.

The power to the aux. Bat. had shorted, then cut right through it's insulation, then through the insulation to the next wire, the wiper power wire, which it energized.

You might "nerd out" on it and check that wire with 9V between your PCM and CPS plug. Has anything shorted recently?



Look here> http://www.jeep4x4center.com/knowled...x.htm#catalogs

Or here, (Thanks Freedgr, (I think) > http://jeep.zerok.ru/index.php?page=XJ
No to the above "zerok" That 88 CPS is different than the 91. (changed after 90)

Bullstang360

It didn't short but my rear wiper quit working a few months back but I just attributed that to the motor burning out. No fuses have popped.

DFlintstone

I found a wiring diagram for 93 OBDI . I was able to save the file but it's to big to post. (43KB?). If you want to post or PM me your Email I'll give it a shot! OK, I checked, it's 420 KB of PDF.....

DFlintstone

It looks like grey/blue is the CPS in to the the PCM.

Bullstang360

Its dark out I'll pull it all apart tomorrow. Also pm sent.

DFlintstone

Sent it. Just in case you didn't know.

IF YOU HOLD THE CTRL BUTTON, THEN PUSH "+", IT WILL ZOOM IN ON WHATEVER IS ON YOUR SCREEN.