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94 Jeep No Injector Pulse
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cj7365
Novice
Nov 15, 2010, 8:15 PM
Post #1 of 9
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94 Jeep No Injector Pulse
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1994
Jeep
Cherokee
4.0
166,000
When I bought this cherokee it started up, but did take a while to start, ran rough then idled out, I had to trailer it home because of a kaput transfercase, I put a battery in it, drained to fuel tank of old fuel, replace fuel filter, tried to start it and it will not start, cranks fine, has spark, and has 40lbs pressure on the fuel rail, I put a noid light on a few of the injector connectors and I have no light, there are no check engines codes just the normal 12 and 55, I can hear the fuel pump when I turn the key on, when I pull the spark plugs they are dry and no smell of fuel. If I spray some starting fluid in the air intake it will run, I have checked 3 ground cables, one on the passenger side of the block, the one on the rear of the head and the ones on the drivers side fender by the PCM, also I have changed out PCMs, I took this PCM and it works fine in my other 94 Jeep. I am really stump on this
Thanks in advance
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Sidom
Veteran
/ Moderator
Nov 15, 2010, 8:40 PM
Post #2 of 9
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Re: 94 Jeep No Injector Pulse
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A couple of quick tests.
1st test your noid light. put one end to batt + & the other batt - and it should light up, if not get another noid light...
Next disconnect all the injectors and check for pulse....
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cj7365
Novice
Nov 15, 2010, 8:54 PM
Post #3 of 9
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Re: 94 Jeep No Injector Pulse
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I have another 94 Jeep and tested the noid light, it works. Tonite I had all 6 injector wires off, noid light did not light
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Sidom
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/ Moderator
Nov 15, 2010, 9:12 PM
Post #4 of 9
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Re: 94 Jeep No Injector Pulse
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Hook a test light up to the injector power wire and see if you have power with the key on and also cranking, I don't have a diagram handy but it'll be the wire that is the same color on all the injectors, the ones for the drivers will be different colors......
Also for the heck of it, maybe throw a pressure gauge on the rail real quick and verify fuel pressure.....
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cj7365
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Nov 17, 2010, 6:48 AM
Post #5 of 9
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Re: 94 Jeep No Injector Pulse
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Ok hooked up volt meter, I am getting 1.2-1.4 volts on the one wire, on each injector, no difference if i am cranking or not, fuel pressure gage shows a continous 40lbs of pressure, and does not bleed down
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cj7365
Novice
Nov 17, 2010, 5:35 PM
Post #6 of 9
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Re: 94 Jeep No Injector Pulse
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I decieded to go out and check the voltages again, well I am getting different voltages now any range from 1.5 to 2.5, so I start moving the platic cover where the wiring harness is under and I got the voltage to get up to 7.5 volts, so I am pretty sure I have some kind of short in there. Tomarow I will start to undo the fuel injector wire harness, at least now I am getting somewhere, I will let you guys know. I hate when daylight savings ends Not sure if I am going to get any sleep tonite.
Sidom thanks for the tip on checking the voltage
(This post was edited by cj7365 on Nov 17, 2010, 5:37 PM)
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cj7365
Novice
Nov 18, 2010, 6:11 PM
Post #7 of 9
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Re: 94 Jeep No Injector Pulse
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Well after uncovering the britle electrical tape and finding the fuel injector wires, I noticed where it makes a 90 degree turn to the firewall the insulation and wires had be broken, where the splice was (6 wires into one) is where the 90 turn to the firewall was. It was stillin the factory splice heat shrink.
when I found the main Power Fuel injetor wire I put a meter on it, It read 7.5v with the ignition on, I was still concerned that I did not have 12 volts, not sure I am supposed to? So I re spliced the wires (temporarily) hooked up all the sensors, and connected the noid light and cranked it, the noid light flashed while cranking, so I hooked everythng up, and the Jeep fired up and runs perfectly.
Thanks to everyone that gave the tips to solve this issue, this by far was the most frustrating for me.
Rob
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Sidom
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Nov 18, 2010, 6:58 PM
Post #8 of 9
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Re: 94 Jeep No Injector Pulse
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Good job on tracking down the problem. Sorry I didn't get back to you sooner, a little crazy around here right now.
Looks like you have things well in hand all by yourself.
You should have 12v at the injectors so you may have another bad wire or something pulling your voltage down... The best way to track this down would be to check for a voltage drop on the circuit while it's energized. You already have the volt meter, if you aren't familiar with the process just google voltage drop testing and there should be some good articles that could explain it a little better than I could....
Here is a system diagram that may help you out...... As you can see the ASD relay powers a lot of stuff.... You may get lucky & just have a bad relay, my luck is never that good......
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cj7365
Novice
Nov 19, 2010, 7:19 PM
Post #9 of 9
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Re: 94 Jeep No Injector Pulse
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Sidom,
Thanks for clarifying to voltage at the injectors, I figured it should be 12volts, but wasn't sure, I will google the voltage drop testing, swap the ASD relay and check the voltage and then go from there, thanks for the wiring diagram
Thanks again.
Rob
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