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Unread 01-31-2014, 04:04 PM   #1
blackyj80
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1987 YJ Wrangler 
 
Join Date: Jan 2014
Location: Dublin, GA
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yj 2.5 tbi won't start

I NEED help. I have a 87 yj with a 2.5. I got the jeep and it was not running. I have been putting it back together and I am trying to start it. I have fuel and fire. It has 120 psi on all 4 cylinders. I have put #1 on tdc and checked the distributor and it is on #1 also. It will not even try to start even if I spray starting fluid in it. I am about to pull my hair out with this thing. I have fire, fuel and compression but will not start. Does anyone have any suggestions.

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Unread 02-01-2014, 06:48 AM   #2
WDNewman
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I would guess it is more than likely your crankshaft position sensor.
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Unread 02-01-2014, 07:17 PM   #3
blackyj80
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Thought about that. Call me dumb but every thing I have read about the crankshaft sensor when it goes out you lose spark and fuel. Will it still pick up and I have fuel and spark just not at the right time. I don't know and have never messed with a jeep like this.
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Unread 02-01-2014, 08:18 PM   #4
crackedcornish
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if you have fuel, spark, compression, and air...it must be the timing. you're probably off at the distributor ... do a complete revolution on the crankshaft, swap the plug wires around so the number one spark plug lead is now where the rotor is pointing, and see
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Unread 02-01-2014, 08:27 PM   #5
blackyj80
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already checked that 3 times. is right
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Unread 02-01-2014, 08:57 PM   #6
jcmooreusmc
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I'm sure you've checked this, but are you certain you set tdc on the correct stroke? Reason I ask is I got in a hurry and did this before and wound up 180 degrees off. Good luck, hope you get it figured out.

Never mind, just saw the last post, so I guess you checked it.
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Unread 02-05-2014, 06:36 PM   #7
blackyj80
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1987 YJ Wrangler 
 
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Ok got another question. I was messing with the jeep again this afternoon. I not have a nice blue spark, I have a yellow spark at the plug. Could that be causing it to not start.
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Unread 02-07-2014, 06:12 AM   #8
Que89YJ
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1989 YJ Wrangler 
 
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The ignition coil module is probably bad. I sent a PM with the Factory Service manual to you. You need to run through the adjustments for the throttle position sensor, Idle adjust motor, wide open throttle switch, and fuel pressure. They are critical on your jeep.
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Unread 02-22-2014, 07:27 PM   #9
blackyj80
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sorry I have been gone from the house for a few week. Thanks for the links. I am going to loot at them tomorrow and see if it helps me out. I have gotten the jeep to crank up but it runs like crap. It seems to be trying to back fire through the tb.
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Unread 02-26-2014, 05:26 PM   #10
blackyj80
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I looked at the service manual and they are going to be very helpful. THANK YOU!!!! I did get it to crank up yesterday by accident. I was messing around with the CPS and bumped a vacuum line for the break booster off the intake and did not know it. When I went to try to crank it fired up. It jumped up to 2500 RPM and stayed there. After a few mins it started running bad and back firing through the TB. I shut it down to look for a anything that would cause it to run so fast. When looking for vacuum leaks I found the hose that I knocked off. I put it back on and tried to crank it up. NOTHING I took it off again and it fired right back up. As soon as I hooked the hose back up it tried to shut back off. I can stick my finger partly over the end of the hose and it will idle back down. Ok the question is WHY will it not run with out a vacuum leak.
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Unread 02-26-2014, 07:16 PM   #11
Que89YJ
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1989 YJ Wrangler 
 
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It's probably the idle motor. Run the adjustments on the isa, wot, and tps. Check the map sensor but my bet is the isa.
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Unread 02-27-2014, 07:24 PM   #12
blackyj80
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Ok well update on the black yj PILE OF JUNK. I got home about lunch today with a bunch of vacuum lines, tees, PCV valve, O2 sensor and clutch master cylinder. I spent all afternoon replumbing the whole truck with all new vacuum lines with new PCV. I replaced the O2 also. Cranked it up and it does idle like it is suppose to now. It ran great for about 3 mins then it started back firing through the tb again. It seems to be backfiring worse than it was when it was idling over 2000. When it starts backfiring it goes to skipping and goes to running so bad it almost shuts down. I have not yet had a chance to test all the sensors yet but I have found the test procedure for all of them so Sunday when I get home from out of town Im going to start working on that.
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