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Unread 03-25-2014, 07:56 PM   #46
sparkieCHB
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Got her running, tested the cam sensor again but my Chilton's is a little vague on the voltage readings. I am getting 9.4v constant while back probing one wire, an alternating 5v to 0v depending on the index of the distributor shaft at another wire, and the final wire is a ground. My Chilton's just says I should have more than 5v constant, I have 9.4v so I'm not sure if that much over 5v is acceptable. But it is sending a consistent 5v to 0v signal back to the computer so I'm am assuming it is functioning properly. Let me know if I have missed something here

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Unread 03-25-2014, 08:23 PM   #47
ZeeJay1997
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1997 ZJ 
 
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the cam sensor is on the 8v sensor circuit from the pcm. i dont know what the acceptable range is for this output, but 9.4 sounds high. (is your meter accurate?) this is the same feed for your crank and speed sensors.

it's worth looking into. if the pcm is expecting an output generated by 8v, you could be getting high inputs from the sensors.

try this:

leave everything connected, back probe the crank sensor on the wt/bk and bk/bl wires. turn the key on and read the voltage. it should be around 8volts. if you're reading the 9.4, disconnect the cam sensor and speed sensors one at a time and see if it drops to somewhere around 8.

do the same thing but measure at cam sensor and disconnect the other two.

if it does drop to 8, you've found the bad sensor.

dont use the block/chassis ground for the low reference. use the bk/bl wire (sensor ground)
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Unread 03-25-2014, 09:23 PM   #48
sparkieCHB
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Quote:
Originally Posted by ZeeJay1997 View Post
the cam sensor is on the 8v sensor circuit from the pcm. i dont know what the acceptable range is for this output, but 9.4 sounds high. (is your meter accurate?) this is the same feed for your crank and speed sensors.

it's worth looking into. if the pcm is expecting an output generated by 8v, you could be getting high inputs from the sensors.

try this:

leave everything connected, back probe the crank sensor on the wt/bk and bk/bl wires. turn the key on and read the voltage. it should be around 8volts. if you're reading the 9.4, disconnect the cam sensor and speed sensors one at a time and see if it drops to somewhere around 8.

do the same thing but measure at cam sensor and disconnect the other two.

if it does drop to 8, you've found the bad sensor.

dont use the block/chassis ground for the low reference. use the bk/bl wire (sensor ground)
Thanks man, I feel like I may be getting somewhere now.

I will get out there and try that, I was looking at the engine wiring schematic I have and it references the vehicle speed sensor but I can find no info on the sensor or how to test it in my s***ty Chilton's. I'm guessing this is the sensor on the transfer case?


EDIT** I was just thinking about it and the ABS light is on all the time. I got as far as switching the relay for it and decided to hell with it, the poor running condition needed my attention worse.

Could the VSS be causing the ABS light? I'm thinking an issue with the harness to the VSS may be causing irregular voltage at the cam sensor. Could a faulty VSS alone be the culprit?

I'm not sure if it is pertinent information but cruise control works, I don't know if the VSS communicates with the VIC to establish gas mileage or not but the VIC did not work when I got the jeep, I have pulled it out and was planning on replacing it. The wiring to the VIC is in good shape but when I pulled it out the VIC itself smelled like the board inside burnt. Again I don't know if any of that matters but I thought it may be worth mentioning
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Unread 03-26-2014, 05:37 AM   #49
ZeeJay1997
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Quote:
Originally Posted by sparkieCHB View Post
Could a faulty VSS alone be the culprit
it could be. i dont see on the diagram where ABS takes the VSS output. the vss is a pulsed DC output so its not an exact science to check it with a meter.

instead of trying to test the output, use the method i outlined and see it it has any effect on the cam and crank sensors.
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Unread 03-26-2014, 11:23 AM   #50
sparkieCHB
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Hit the VSS, cam and crank sensors with the meter again. Getting 9.3 constant to all three and unplugging any of the sensors while testing any one does not alter the number. After back probing the white/black wire at the PCM connector, I found I have 9.3v coming directly out of the brain. WTF??? If I need to I will warranty out the PCM, does everyone think 9.3v is an unacceptable amount over the 8v supply I should be getting?
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Unread 03-26-2014, 12:24 PM   #51
sebian
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Just to throw it out there, have you checked your ignition coil? Low/bad spark would cause you to not ignite, and burn, the fuel properly. You can check the resistance on the coil, should be rather low resistance. Chilton's should have the spec for it.
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Unread 03-26-2014, 05:13 PM   #52
ZeeJay1997
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see what the voltage does when cranking and running

the 5v toggle you're seeing is normal, so maybe the 9.3 is not an issue. all three sensors are hall effect.

may be time to focus elsewhere.

do the same tests on the 5v sensor reference at the tps
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Unread 03-28-2014, 03:38 PM   #53
sparkieCHB
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Thanks for all your help Zee, I took a pretty good digger off of an extension ladder yesterday and will be on crutches for the next few days. I probably won't get any further on the jeep till I can stand on two feet again. I pulled the fuel rail and injectors and are cleaning them out right now, after I reinstall the rail and injectors I'll hop back on here and run through the TPS portion of the harness. I'm also I going to take a close look at the coil, I may even have a spare to swap it out with, I just need to dig through my bucket of jeep inventory.

Thanks again for all the help everyone, hopefully I'm close to fixing the the turd
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Unread 03-29-2014, 05:56 AM   #54
ZeeJay1997
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bummer about the fall. sux to be gimpy. look around on you tube for different ideas on how to check sensors.
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Unread 03-29-2014, 08:12 AM   #55
sparkieCHB
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I found out my buddy has a OBD 1 chrystler DRB scanner so I'm going to borrow it from him, hopefully I can see something freaking out with the scanner hooked up. I'm starting to think it is something simple and I'm just chasing my tail with the other stuff. I'm going to pull the plugs later today and take a look to see if one cylinder looks like the plug is burning really hot or if any of the plugs are wet, I may have a pintle on an injector stuck partially open or something.

I have a set of Chevy tpi 350 injectors at the house that are good, if I have to (and I am able to) I'll swap them out and see what kind of difference it makes
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