TajMan Posted October 6, 2007 Share Posted October 6, 2007 I got my '87 Comanche Pioneer w/ 4.0 I6 broken, been sitting for 2 years. Person I got if from had driven it 20 miles to his house originally, running on 5 cylinders. (1 pushrod was off & valve spring broken, head was a mess in that cylinder) I finished a head rebuild. Tried starting for 1st time and it wouldn't crank. Cleaned tranny NSS and got it to crank. now I wasn't getting spark Electrical kind of a mess, previous owner bought an 87 Cherokee engine wiring harness on eBay which I had. I ended up swapping out that entire harness, just finished. Cleaned up wiring just a little. Plugged in some unplugged connectors, spliced 1 wire I found melted under the dash and it hasn't melted again with battery connected now. Ok try again. STILL NO SPARK! With the key in ACC position, the yellow wire on the 3-terminal connector on the coil has +12V, like mechanic friend informed me it should. Where can I turn to diagnose now? I've done so much damn work on this thing and have yet to drive it. It only has 113K miles, auto tranny. Link to comment Share on other sites More sharing options...
optichris Posted October 6, 2007 Share Posted October 6, 2007 I don't have a 4.0L, but I know that a bad/foulded/disconnected crank position sensor will cause a no-spark condition. The ECU waits for the crank position sensor to tell it where the motor is, and then fires at the appropriate time...no crank position sensor, no fire. Just an idea. Link to comment Share on other sites More sharing options...
TajMan Posted October 6, 2007 Author Share Posted October 6, 2007 Yes already been there, crank position sensor was disconnected- then I got it plugged in the right spot. Crank position sensor can go bad, but I need a proper line of diagnosis, not just randomly replacing parts until it works. Link to comment Share on other sites More sharing options...
Eagle Posted October 6, 2007 Share Posted October 6, 2007 Somewhere someone posted what the CPS should put out when you crank the engine over. Basically you disconnect the CPS and put a digital multi-meter between the two terminals. I think it's supposed to generate 0.5 volts or something like that. An '87 will be like my '88, with the wires from the CPS to the ECU going through the C101 connector on the firewall. The factory has a kit to bypass that with a replacement harness direct from the CPS to the ECU. I'd recommend it. Link to comment Share on other sites More sharing options...
Wildman Posted October 6, 2007 Share Posted October 6, 2007 No spark is generaly the CPS, first sensor to check, Also there is a CAM sensor the will kill the spark, and the netural safty switch (No crank, which you found). Check this site out, tell how to check each sensor, and spects. http://www.lunghd.com/Tech_Articles/Eng ... ostics.htm With you changing out the entire wiring harness, it might be worth it to take a brake, and then re-check every connector. Just one loose, not connected will cause problems. [ 0.5-0.8 VAC while cranking - I had to check, Eagle :D ] Link to comment Share on other sites More sharing options...
TajMan Posted October 7, 2007 Author Share Posted October 7, 2007 I did my best testing the CPS with half-broken volt meter, taped to my windshield facing down so I could test/read it alone. Don't think I get quite 275ohms resistance, or ANY voltage fluctuations while cranking. I'll replace the thing and go from t here, soon enough. $45 for new sensor, I'll probably be trying some junk yard sensors first for min. $ Link to comment Share on other sites More sharing options...
Wildman Posted October 8, 2007 Share Posted October 8, 2007 I would think a new digital multi-meter would be the first purchase, HF has them for $2.50. I would not trust a junk yard CPS, plus getting it out......not worth it. Check here - http://www.rockauto.com/catalog/x,carco ... ttype,7196 New CPS for $32, but another member here wrote couple weeks ago that he had problems with an after market CPS, and ended up getting one thru the dealer :dunno: Link to comment Share on other sites More sharing options...
TajMan Posted October 8, 2007 Author Share Posted October 8, 2007 Friend I got the Jeep from gave me a new multimeter. Thanks for that link, which part is it the $31.79 or $32.79? Link to comment Share on other sites More sharing options...
Wildman Posted October 8, 2007 Share Posted October 8, 2007 I would go for the AC Delco #2132565 Reason I said to get a new multi-meter, you need something that will give a good/true reading, no guesting when it comes to testing the sensors. Plus it's a tool you'll use over and over again. ;) Link to comment Share on other sites More sharing options...
TajMan Posted October 8, 2007 Author Share Posted October 8, 2007 Hehe, I printed out that site and brought it in, got Checker to give me the sensor for $33 total. We shall see... Link to comment Share on other sites More sharing options...
TajMan Posted October 9, 2007 Author Share Posted October 9, 2007 Its very easy to drop the top bolt from the sensor INTO the tranny bellhousing isn't it. It dropped somewhere, can't find, then realized from above that the hole's right there underneath it. If you remove the shield on the bottom front of the tranny, does the bolt fall down past the TQ easily so you can grab it? Link to comment Share on other sites More sharing options...
Wildman Posted October 9, 2007 Share Posted October 9, 2007 If you remove the shield on the bottom front of the tranny, does the bolt fall down past the TQ easily so you can grab it? On an automatic, maybe, if your lucky. Link to comment Share on other sites More sharing options...
TajMan Posted October 9, 2007 Author Share Posted October 9, 2007 Tip for those in future: Take that shield half-off, use a piece of tie wire fishing around in gap along bottom of flywheel, you'll be able to get that bolt out. I did it TWICE lol New CPS installed, I used volt meter and cranked engine over again. IT DOES NOT SHOW ANY READINGS as engine goes around! Maybe like the bad one, needle moves ever so slightly up and stays there while cranking--but not pulsing and not .5V. Possible that I need a slightly different part number than the new Niehoff sensor that I got? Link to comment Share on other sites More sharing options...
TajMan Posted October 10, 2007 Author Share Posted October 10, 2007 BUMP any differences in new sensors that could cause one still not to read anything? Link to comment Share on other sites More sharing options...
Eagle Posted October 10, 2007 Share Posted October 10, 2007 New CPS installed, I used volt meter and cranked engine over again. IT DOES NOT SHOW ANY READINGS as engine goes around! Maybe like the bad one, needle moves ever so slightly up and stays there while cranking--but not pulsing and not .5V. Needle? You have an analog voltmeter that reads to half a volt? I think you need a digital meter. The pulses are going to be faint and quick ... I doubt that an analog meter can even swing the needle fast enough to register them. However -- did you ever have this truck running? Do you know that the CPS mounting bolts are the correct, original bolts? The correct bolts have a solid (unthreaded) shank where they go through the flange of the CPS, in order to locate it accurately. If a previous owner dropped a bolt and replaced it with something out of his miscellaneous bolts pile, chances are it's threaded full length and doesn't hold the sensor in the correct relationship to the flywheel. Link to comment Share on other sites More sharing options...
TajMan Posted October 10, 2007 Author Share Posted October 10, 2007 I had good analog volt meter testing so a 1.5 volt battery would swing the needle 1-2 CM, but on the CPS cranking it moves up maybe .5 MM Car was running when parked 2 years ago. Yes they are the correct bolts holding the CPS with that "shank". Link to comment Share on other sites More sharing options...
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