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'96 Grand

530 views 6 replies 3 participants last post by  MKCoconuts 
#1 ·
'96 Grand, 5.2L. So the other day went to move my Jeep so my friend could wash his truck, Jeep would not start. Just cranked and cranked. Pushed it in the garage and have been going through things. Found no spark coming from the coil. Thought maybe it was the crank sensor so replaced that (btw, if any one knows the engineer that thought up it's position, PM me, I have words for him/her). Still no spark. Checked the dist cap and button since I just need a tune up the week prior, all looked fine. Tried coil off the spare 5.2 that I have at my parents house. Still no spark.

Checked voltage to the coil, I am reading 6-7 volts coming to the coil. I know it should be 12 volts. Checked signal wire with a light up probe and with the probe grounded to the battery, it lights up when you crank the ignition but I was under the impression it was supposed to flash (like a strobe light). I am going to try and trace the wiring back to the PCM for any damage. Is there anything else I should look at? Any one have any idea what wires at the PCM I should check?

I am honestly thinking the PCM took a crap. I had this Jeep do it a few weeks after I bought it and I'm pretty sure it did this very same thing. I was lucky back then I had a spare computer from a '97 that I could use. I don't want to go spending money on a used or reman'd PCM until I at least 95% sure that's what it is.

I'm not in a huge hurry to fix this as I'm temp laid off (due to the virus) but it'd be nice to have it figured out in case I want to go for a Jeep ride or something were to happen to my other two vehicles. Thanks in advance guys!
 
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#2 ·
Checked voltage to the coil, I am reading 6-7 volts coming to the coil. I know it should be 12 volts.
When are you checking and what terminal? You should have 12V+ at one of them for only a few seconds after turn the key to run and when cranking. Do you hear the fuel pump prime? Any codes? If the pcm was bad you probably wouldn't even show the 55 code meaning end of codes.

https://www.quadratec.com/jeep_knowledgebase/article-24.htm
 
#3 ·
I'm checking the white wire, which should be 12V+ when cranking and only getting 6-7 volts, I will double and triple check this both while cranking and with the initial key on.

I can hear the pump prime and no codes have come up. I tried with a scanner and also did the key on/key off trick. Showed code 12 and code 55 where the odometer reads. My SES light does not work, either it's missing the bulb or it's burned out. But I would suspect that whatever codes would flash, would still pop up with a scan tool?

It just blows my mind that it was literally running fine, sat for less than 12 hours and then all of sudden wouldn't start.
 
#5 ·
I will be double checking voltage here shortly....but last night it was showing 6-7 volts at the coil, but I honestly do not remember if that was with just the ignition on or if that was while cranking.

The injectors feel like they are pulsing, but I will verify 12 volts at them as well. I am also going to test the cam pick that's in the distributor and make sure it is getting signal.

Did not check fuel pressure with a gauge but there is pressure at the rail (pushed in schrader valve and got blasted). But lack of fuel does not seem the issue as I stated in the original post, there is zero spark coming straight off the coil.
 
#6 ·
do not worry about CMP at this time.
we can check at injectors easier, and an issue would set a code.

KOEO= Key On Engine Off - some of the 12v will only be energized for @3 seconds
 
#7 ·
Figured it out. Checked the CMP any ways, it was good and getting signal. Next, we moved back to checking voltage to the coil...and this is where the info I had was wrong. I was told that the white wire should have 12V+ when cranking. Well it didn't. So I checked the green/orange strip wire and hey, we have 12V+ there! Okay, found another write up on how to check the coil and so I followed that and found the original instructions I found had everything backwards. Green is 12V+, white is signal. Using a 12V test light, I connected it to signal wire and cranked. It flashed. Long story short, it was the plug to the coil that was causing and issue. It got damaged once before and the solder must have worked loose causing the no start. Kinda feeling dumb now.
 
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