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Unread 06-17-2008, 07:56 PM   #1
redrcks
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1991 YJ Wrangler 
 
Join Date: Jun 2008
Location: MI
Posts: 14
91 YJ New computer & still not starting consistently

Help.. I am a newby jeep owner.. I just got this one from OH. I knew it had some issues, but not nearly as many as it has. I just replaced the computer on my YJ and I am still experiencing no spark.. It ran great right after I installed it. Then after about 20 min or so, I just quit while I was driving.. No spitting, sputtering.. just silence. Now, we can't get it to start again. She turns over though. The coil was good, plugs etc.. Please help!

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Unread 06-17-2008, 10:57 PM   #2
TSEJEEPERS
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1993 YJ Wrangler 
 
Join Date: Dec 2003
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We need more information fill out your profile it will help.
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93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list. www.mijc.org
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Unread 06-18-2008, 05:45 AM   #3
golfcartdoc
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Same problem here. 1991 jeep renegade 4.0, new computor (boy they sell a lot of computors) no fire and I have replaced EVERYTHING. I am heading to the stealership again but they seem to be lost themselfs! Didn't mean to steal your post, just waiting for a new direction.
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Unread 06-18-2008, 09:19 AM   #4
TSEJEEPERS
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I would check or replace the CPS also check the wires going to it.
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93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list. www.mijc.org
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Unread 06-18-2008, 08:05 PM   #5
azgurney
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1991 YJ Wrangler 
 
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Several years ago i replaced my CPS with a napa unit because I wanted to have a spare and thought I would put on the napa sensor to make sure it worked ok. Shortly after this it stalled on a trail and would not start. I started checking obvious things with no results. I tried starting it one more time and it ran fine. A short time later I after filling up at a gas station it would not start. Again after a while it started just fine. I decided to put the original cps back on and have not had a problem in several years. I still have the napa cps as a spare but they can cause intermittent problems. If you plan to keep your Jeep I would buy a new cps at the dealer.
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91 Wrangler 4.0 5sp
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Unread 06-18-2008, 08:15 PM   #6
Brandon_YJ
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I've herd it said before that if you are wanting a part for longevity get an OEM part because they are made to last more than aftermarket and/or performance ones.
Not sure how true that is, but it sure seems fitting in your case.
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Originally Posted by azgurney View Post
Several years ago i replaced my CPS with a napa unit because I wanted to have a spare and thought I would put on the napa sensor to make sure it worked ok. Shortly after this it stalled on a trail and would not start. I started checking obvious things with no results. I tried starting it one more time and it ran fine. A short time later I after filling up at a gas station it would not start. Again after a while it started just fine. I decided to put the original cps back on and have not had a problem in several years. I still have the napa cps as a spare but they can cause intermittent problems. If you plan to keep your Jeep I would buy a new cps at the dealer.
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Unread 06-19-2008, 07:47 AM   #7
redrcks
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1991 YJ Wrangler 
 
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Addition to Saga..

Well. Still the jeep sits. Still won't spark. Went and got an MSD ignition for it. Parts store said it would be a waste. I also ordered a CPS. Took the old one off, no sign of wear. Wires still in good condition. Will still replace it. I heard that this is my main reason for malfunction. So tonight, we will see if installing the CPS makes her run.. New computer, new CPS. Distributor and coil still are at proper ohms.. (what is proper anywas?). Plugs seemed to be in very good condition when we got it.

I am also having rod knock issues. Replaced the main and rod bearings w/ .010 OS. Used Plastigauge appeared to be fine. She still knocks. The previous owner or so said that it was a rebuilt engine. The rods are stable, no play. The crankshaft however has a bit more play than specs recommend. Sounds like the knock is coming from the front only. Main bearing #1 was pretty rough when we replaced it. Decided to drive her until we officially know what we are going to upgrade the crankshaft to. We would like to get a heavier one..

Currently I do not really have anything else to add to my profile. She is all stock except for headers right now, want to make sure she will run properly before I do any work like that too it. I have a 4" rough country suspension lift for it. Won't replace the tires until they go. Probably next summer. Have some new door skins in route. Will start cutting out rusted body parts and welding in some heavy steel.

Thanks
S
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Unread 06-19-2008, 08:03 AM   #8
Delta347
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I own a 1990 so I have a slightly different situation (fixed mine in 1 day since I had the parts and the sacrificial assistants to get caught on fire instead of me).

All stock in the engine minus battery and the fact i have a Nutter Bypass (e.g. no computer since I have a carbuerator).

Fixed my timing late monday and she ran better after that than in months. Next morning dies on the freeway and won't start. AAA towed it back to the house and I called in the cavalry.

12 hours of work we tested distributor, the sparkplugs, the wirings, we LED Light tested the power cables going TO the coil.

Now note my engine would rotate, and click, but wouldn't catch and run.

So we tested to see if when the cable from the coil to the distributor was placed near metal if it would ARC. (this was after we determined the coil had power). Nothing, so we put in a new coil (well a used one but for a YJ thats new). Tried cranking her again, still nothing but now the coil worked.

Tested to see if the spark plugs were getting power by doing the ARC test on the cables from the distributor to the spark plugs. They arc'd so the coil was working fine.

We decided to check the FUEL PUMP. Now I have a 1990 once again so my mechanical one is on my crankshaft in the engine luckily, but I had an electrical one mounted parallel to it (which turned on and ran BUT WASN'T PUMPING NADA!!!) so we disconnected the electric fuel pump and put it on the mechanical stock one.

Hmm still nothing, but at this point we were guessing it just couldn't crank enough to get gas flowing at this point so it needed a 'jump start'. We took the cover off the carb and filter and proceeded to pour gas directly into the carb. At this point the engine backfired or sparked ackwardly catching the bottle of gas on fire along with my good friends foot:



Long story short. I would just to be safe check that your fuel line has gas flowing through it. If that doesn't work light part of your engine and you on fire, Jeeps like to work when the human suffers. (DO NOT TAKE THE PREVIOUS STATEMENT SERIOUSLY )

So in the end my advice is:

Check that the fuel line has flow. (just disconnect part of it in the engine and hold it over a cup while you try to start your jeep)

If you DIDN'T replace the coil, check that it causes arcs when exposed. (But I assume your replaced the coil, distributor, sparkplugs, and computer from what you said).


And the final moral(s) of the story are:
Jeeps like watching their owners and owner's friends suffer.
Fire is our friend.
Check even the non-electric aspects of the problem. (Since not only did I have an electric problem, but my gas failed too)[my guess is that I had a surge in my power since an electric fuel pump and coil gave out at the same time.]
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So ghost has a plug in his hole and opihi has a gaping hole, Do I need to worry about this hole at all? I just don't want to start her up and have something spewing out of it.
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Unread 06-19-2008, 08:30 PM   #9
redrcks
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Round What? 91 YJ new computer, new CPS... now what

So, we replaced the CPS today and with quite a few taps on the gas (FI), she finally started.. quit right away, then started again.. had to keep on the gas for a little bit to keep her running.. YAH I said.. Well, took her for a test drive and now NO power.. Should I of thought any different? lol All wires had spark. When I took the old plugs out, we noticed that 4,5,6 were a little hotter than the rest.. Replaced the plugs anyhew jic. Still now power..

What did we do? It idles fine, and doesn't hesitate when gas pedal depressed. It runs smooth. I just can't get past 30 mph. It was in 2Hi. Can it not be pumping enough fuel now for some reason? Keep in mind, she ran great before we started touching her,then we took out the alarm and wired back to original. Coil tested fine too, before CPS installation (have not tested the coil since). Distributor was in good condition as well. All relays are fine.

Thanks.
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