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SPARTAN LOCKERS are on sale BIG TIME at ROCKRIDGE 4WD!FLASH SALE! Open thread to reveil the Newest Sale @ ROCKRIIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

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Unread 10-09-2014, 12:17 PM   #1
mattcopeland198
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1998 ZJ 
 
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No start

Back again guys, I hope this isn't a useless new thread but here goes....


Going to pull out of the driveway in my 98zj 5.2 and it died. tried starting again and no go. it turns over but no start. i checked the fuel pump and fuel bar and its got good pressure and fuel at the injectors.

One thing i noticed is that when i turn the key on, the battery gauge reads nothing and the gas gauge reads nothing(even though there is half a tank). odd

after doing some research on her i began to suspect the crankshaft position sensor, changed it out (biggest pia job ever) to no avail. i am considering replacing the camshaft position sensor but i would like to know if there is something else i should be looking at. Any help is greatly appreciated and let me know if there is more information you need. Cheers

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Unread 10-09-2014, 03:28 PM   #2
ZeeJay1997
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those two gauges take the PCM input from the CCD bus. This, coupled with the fact that you have fuel pressure means the PCM is partially inop. It could be an internal problem or an input or output is shorted causing a partial shutdown.

most commonly, the o2 sensors or wiring short causing the pcm to stop working or more uncommon, cause it to go wonky. try disconnecting the o2 sensors and see if the gauges start working.

click the green link below and check the items under #1 that can cause a PCM misdiagnosis.
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Unread 10-09-2014, 04:20 PM   #3
mattcopeland198
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Quote:
Originally Posted by ZeeJay1997 View Post
those two gauges take the PCM input from the CCD bus. This, coupled with the fact that you have fuel pressure means the PCM is partially inop. It could be an internal problem or an input or output is shorted causing a partial shutdown.

most commonly, the o2 sensors or wiring short causing the pcm to stop working or more uncommon, cause it to go wonky. try disconnecting the o2 sensors and see if the gauges start working.

click the green link below and check the items under #1 that can cause a PCM misdiagnosis.
Thanks for the info sir....could a transmission fluid leak cause those sensors to be shorting out?
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Unread 10-09-2014, 05:41 PM   #4
ZeeJay1997
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Quote:
Originally Posted by mattcopeland198 View Post
could a transmission fluid leak cause those sensors to be shorting out?
not likely
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Unread 03-19-2015, 12:11 PM   #5
mattcopeland198
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Quote:
Originally Posted by ZeeJay1997 View Post
not likely

Thanks for the info, sorry for taking so long to get back.

Here's the update: Upon closer inspection of the O2 sensors, I noticed the rear sensor's wire was touching the rear driveshaft (dumb I know) and the wire coating has completely rubbed through. One of the wires was cut completely the other is just exposed. Needless to say they probably touched. I unplugged both sensors and checked the fuses under the hood/dash. Found one 20 amp fuse under the dash that was blown and replaced it. turned the key to the on position to see if the gauges would work but still no good. So where from here?

Obviously I need a new O2 sensor. But could those wires touching have done some other damage? I pulled the ecm and opened it up for a visual inspection and everything looks to be in order. No burnt smell,discoloring. I know that doesn't automatically mean it isn't damaged though.

Also, when I checked to see if the gauges would work (with the o2 sensors unplugged) I also had the Crank position sensor unplugged. Does that need to be connected for the gauges to work?

Again, thanks for the help
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Unread 03-19-2015, 12:23 PM   #6
PolkaPower
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Those wires can short out the PCM.
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Unread 03-19-2015, 12:31 PM   #7
mattcopeland198
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Originally Posted by PolkaPower View Post
Those wires can short out the PCM.

How do I know if that is the issue? do I just have to bite the bullet and replace it or is there someway to verify it through troubleshooting first?
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Unread 03-19-2015, 01:34 PM   #8
PolkaPower
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It's never happened to me before but someone here will be able to tell you. Where is Coralman or Uniblurb at?
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Unread 03-19-2015, 05:44 PM   #9
mattcopeland198
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update.....


the fuel pump is not priming when I turn key to on position.

also, hooked up a scan tool and it won't read anything. Seems like signs are pointing to the pcm but before i replace it I just want to make sure there isn't something else I should be checking. Any help is greatly appreciated. You guys rock
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Unread 03-19-2015, 06:19 PM   #10
ZeeJay1997
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just be sure you've identified all of the damaged wire and isolate it from the adjoining wiring and ground. then be sure the fuse didnt blow again.

when those wires get shorted, it's luck of the draw as to what kind of damage it will do. it depends on what shorted to what and for how long. There are over current devices built onto the main board in the PCM that can open. This may be the case in yours. So long story short... you probably need a PCM.
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Unread 03-19-2015, 07:28 PM   #11
coralman
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Exact same thing happened to me.A mech left the wires dangling which got into the shaft. Took the pcm out. That was wayback. More recently, I had a new exhaust installed and couple of days later it dawned on me that I better check behind them. Rear 02 was ok, but he had left the front 02 wires off the mounting post. Just lucky. Main reason I do almost all of the work myself. Always check behind them!
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Unread 03-19-2015, 08:04 PM   #12
MrRoundel
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Main reason I do almost all of the work myself. Always check behind them!
Agreed. Always inspect the work that you paid $100+ per hour for someone else to do properly. That agreed-to $100, just might not be enough for them. In other words, they'll be in much more of a hurry than you'd be doing your own work. "Hmm...$100 for 1/2 hour sounds much better. Oh, there's the roach-coach now!"
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