Need help ASAP!!! Unknown problem?? - JeepForum.com

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post #1 of 20 Old 05-15-2010, 08:27 PM Thread Starter
aolitesnsirens
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1991 YJ Wrangler 
 
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Need help ASAP!!! Unknown problem??

I have a 1987 Jeep YJ 2.5l 4 cyl. manual trans. The other day I was driving on the freeway doing about 70 mph when all of the sudden my Jeep just stopped running. The RPM's went from approx 3000 to 0. Luckily, I was able to get it to the side of the road without being hit. I tried to restart the vehicle, but with no luck. After having it towed to my house, I began to seek out the problem the next day. I've done some research and traced the Auto shutdown relay. I've replaced both of them along with the ignition switch under the steering column. No luck. I dropped the fuel tank and pulled out the fuel pump. Then connected it to a 12v battery. Fuel pump works fine. However there is no power to the pump when the key is in the ON or START position. Continuity from the relay to fuel pump is good. All fuses are good. I heard about a possible fusable link. I tried to track it down, but could not find anything. I'm at my whits end and don't know what else to do!! So I figured I'd try posting a thread on this site to see if there is anybody who might know something about this Jeep. It's hard to find a mechanic who knows something about these older Jeeps. Any HELP is apprecitated!!!

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post #2 of 20 Old 05-15-2010, 11:08 PM
moonshinefuel
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Did you check it for codes? I believe the 87 should have the same protocols for check engine light sequences as the later yj's.
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post #3 of 20 Old 05-15-2010, 11:45 PM
93YJfalcon
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edit -nevermind... I got nothing

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post #4 of 20 Old 05-16-2010, 01:13 AM
YJake
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Will it crank at all or not even try to start?

Jake

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post #5 of 20 Old 05-16-2010, 01:17 AM
si-lo
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Might be a dumb question but is your battery still charged? The only time I have ever had something like this was when my alternator went out. Other that I don't really know. Good luck.
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post #6 of 20 Old 05-16-2010, 01:59 AM
89yj2010
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My friend is having the same problem. The fuel pump works if you put a hot wire to it out of the tank but when its back in the tank and the key is on or whatever its not running.
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post #7 of 20 Old 05-16-2010, 03:50 AM
dodger889
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Try jumping pins 30 to 87 and see if it runs then on the fuel pump relay.

A 89 yj with a 4.0 aw4 sye out of an 92xj. Now the hard part is done time to get it up in the air just a bit. Working on 8.8 with 3.73 and lsd for the rear. and new D30 hp with 3.73 .
For those who have not figured this out I'm old school but can handle the new too.
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post #8 of 20 Old 05-16-2010, 04:27 AM
InEmberClad
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Quote:
Originally Posted by moonshinefuel View Post
Did you check it for codes? I believe the 87 should have the same protocols for check engine light sequences as the later yj's.
He's not going to have codes, all he's got is an Emissions Maintenance Timer that's going to light up every so often to remind him that he needs to unplug it and move on.

Have you ever poked around under your dash to see if any POs have made any changes? look for non factory splices or something. They may not have been done right, I had the same problem with my 89 and it ended up being a butt connector that just got jostled lose. Try tracing the wiring from the fuel pump all the way back to the fuse block and make sure everything in there is good.
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post #9 of 20 Old 05-16-2010, 09:23 AM Thread Starter
aolitesnsirens
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I've traced wires back to the fuse box and to the ASD relay next to the battery. Continuity is good. No signs of any loose wires under the dash. There is no Check Engine Light on this type of Jeep. I did find a small black box under the dash with wire plugs on both sides of it. I'm wondering if this is the ECM?? Or if this vehicle even has an ECM where is it?? Haven't tried jumping pins 30 and 87 yet. Will do that when I can. Does anyone know if there is a Mechanic who works on these old Jeeps in the Los Angeles area?? I'm just about done!!!
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post #10 of 20 Old 05-16-2010, 02:25 PM
MLJeeper
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Have you checked the crank position sensor?

Your limited slip differential sucks.

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Any video of the sound?
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post #11 of 20 Old 05-16-2010, 02:31 PM Thread Starter
aolitesnsirens
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Have not checked the CPS. What does that do?? I've been hearing a lot about it, but don't know what that does in relation to the electronics of the fuel pump...
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post #12 of 20 Old 05-16-2010, 02:32 PM Thread Starter
aolitesnsirens
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Quote:
Originally Posted by MLJeeper View Post
Have you checked the crank position sensor?
Have not checked the CPS. What does that do?? I've been hearing a lot about it, but don't know what that does in relation to the electronics of the fuel pump...
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post #13 of 20 Old 05-16-2010, 02:38 PM
MLJeeper
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It will not run if the CPS is bad. Controls timing and wont allow the engine to run. if its bad

Your limited slip differential sucks.

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Originally Posted by Anticanman View Post
Any video of the sound?
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post #14 of 20 Old 05-16-2010, 02:43 PM Thread Starter
aolitesnsirens
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Quote:
Originally Posted by MLJeeper View Post
It will not run if the CPS is bad. Controls timing and wont allow the engine to run. if its bad
Will the CPS control the power to the fuel pump relay??
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post #15 of 20 Old 05-16-2010, 02:44 PM
MLJeeper
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Im not sure, but yeah i think so.

Your limited slip differential sucks.

Quote:
Originally Posted by Anticanman View Post
Any video of the sound?
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