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Unread 05-27-2012, 11:29 PM   #1
y90j
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1990 YJ Wrangler 
 
Join Date: May 2012
Location: keller, tx
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1990 yj will not start NEED HELP!!!

Hey guys new to the forum but ya'll seem to help everyone out effectively hope ya'll can help me as well. I've got a 1990 yj that i recently purchased decided to do a tune up on. It is a 6 cyl all stock under the hood. Before the tune up it was running good except for the fact that if you put the petal to floor it would cut out for a couple seconds before it would rev up and take off. Figured this was a vacuum leak so I did a tune up along with checking lines.

In the tune up I replaced the coil, distributor cap, rotor, plugs, wires, air cleaner, O2 sensor, and oil and filter. Found a leak in the fuel line right before and after the fuel filter so i replaced those hoses and the fuel filter. After all this I drove it to the auto store running better but still with the cut out when you floored it. Got home with some new lines and ran hoses from front pcv back to to decel valve to back side of carb and to the canister. Replaced the rear hose from rear pcv to air filter and reconnected the fuel vent line on the canister that i found unconnected.

Now she won't even start. She turns forever with good battery, good fuel flow, and good spark. I am completely stumped and do not want to start throwing parts at it. Can a vacuum issue cause her not to start or is it coincidental that something else went wrong as i repaired these air hoses?

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Unread 05-27-2012, 11:49 PM   #2
AmmitOsiris
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1990 YJ Wrangler 
 
Join Date: Apr 2011
Location: Brentwood, California
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I have the same problem with flooring it on how it hesitates and or cuts out, I would like to know why this is please help!!!!!!!
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Unread 05-28-2012, 02:41 AM   #3
NonRubicon
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1990 YJ Wrangler 
 
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It seems that parts on the old Yjs go bad in batches, whether the parts are related to the problem or not, so that can't be ruled out.

If the emissions canister is bad, it could create a huge vacuum leak through the vapor vent line to the carb. I've had this make mine run real rough at idle. Try disconnecting the canister vapor vent line and plugging that port on the carb. See if that will get it to start up for you.
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Unread 05-28-2012, 06:16 AM   #4
GatorsUF
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1989 YJ Wrangler 
 
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Just throwing this at the wall:

Try removing both batter cables and touch them together (while they are unattached from the battery) for 10 seconds or so, then reconnect. I was told this resets the ECU, may just need to be reset after you fixed all the leaks...
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Unread 05-28-2012, 06:47 AM   #5
Karma
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HI,
I assume you still have the Carter BBD carb. If you really have good fuel flow AND good spark, then you must be flooding. Try starting it then pull a plug. It should not be wet. If it is then you are flooding. If wet, start looking at the carb for your trouble.

I'm not going to go into all the possible problems you might have with the BBD and the associated emissions system. I've been there and done it. After finally getting the system to work well, I decided it was not worth keeping. I converted to a Howell fuel injection and all issues went away. If you insist on keeping the BBD then prepare for a long learning curve. You should replace all your vac lines (there are a bunch of them!) right away as a starting point. Then check every component in the emissions system.

You should buy a Factory Service Manual. Do not settle for a third party manual. They will not help much. I must warn you that you will be pretty much on your own with the BBD and emissions system. Not many people know enough about the system to be able to help you. I do but I'm not going to try over the internet. Your must learn it yourself.

Your problem may turn out to be simple. Or it could be very difficult. Your success mostly depends on how well you understand the system.

Good Luck, Sparky
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Unread 05-28-2012, 06:57 AM   #6
y90j
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Thanks guys I am going to test all these aspects today and I will keep ya'll posted.
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Unread 05-28-2012, 08:26 AM   #7
y90j
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1990 YJ Wrangler 
 
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Tried plugging the carb form the canister inlet and nothing checked the spark plug after trying to start and dry as nun. Fried my starter however and have to replace that now to be able to diagnose anything. Auto store is really liking me lately. thinking about running a mc carb and getting rid of all these stupid hoses.
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Unread 05-28-2012, 01:10 PM   #8
y90j
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Ok so I replaced the starter and then proceeded to take off the lower air cleaner assembly. After getting it off i decided to try and fire it and it started. Ran it for 5 or 10 minutes and it still cut out when you floored it. Just happy to have it running i turned it off and decided to put it back together for a little while and deal with the cut out. However soon as i shut it off i went to fire it back up and it wont start again.
Im at a loss... is this simply a carb issue and i need to go through and clean it out really well or a vacuum problem or a sensor that could cause this. Why would it start only after sitting for a while. Any help would be much appreciated.
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Unread 05-28-2012, 05:45 PM   #9
Karma
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HI,
I think you are reporting a mixed message. When you say that you are getting a strong spark I assume you are getting a strong spark. If you are then the problem must be a fuel issue.

But I'll, for the moment, assume you are not getting a strong spark all the time. I had an intermittent starting issue with my YJ when I first got it. It turned out to be an intermittent ignition control module. This is located below the radiator overflow container on the drivers side. Auto Zone charges about $65 for a replacement and they seem to be good.

Sparky
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Unread 05-28-2012, 06:13 PM   #10
Fernando
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Dude I think you are having the same problem we all have with the old emissions crap...at some point in life every carbed Jeep comes to this crossroads, do a search for "nutter bypass" and perform this procedure, your problem is with the ignition timing being controlled by the atari 2600 computer in there... that causes the hesitation. As per the problems starting, it must be related to some sensor, however if you start troubleshooting that system you open a huge can of worms... if I were you I would start by doing the nutter, upgrading the ignition with a mod called the Team Rush mod and changing the carb to either a Weber or Motorcraft... run searches for all these mods and soon you will have a roaring Jeep. Best of luck.

One last thing, if you live in Cali find out about how legal these mods are before you do them... I know you are not supposed to tamper the emissions system in any way, just a friendly reminder.
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Unread 05-28-2012, 10:36 PM   #11
NonRubicon
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The OEM setup can be a royal PITA to troubleshoot. Takes a lot of patience and guesswork with the OEM setup. They can be made to run decent though. I tried my best for two years before giving up and swapping in TBI.

If you're going to keep it stock you might want to check out this website:
Adventures Under the Hood
Pretty much the best resource online for the 4.2L setup.
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Unread 05-29-2012, 09:56 PM   #12
y90j
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1990 YJ Wrangler 
 
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Location: keller, tx
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PROBLEM SOLVED!! Thanks for everyones help and input it definitly helped me to find everything that was wrong with her. so here's what happened.

I thought i was getting great spark because i tested the wire off the plug and saw it spark, however i tested it again and the jeep fired up on five cylinders without even hesitating. Thats when i knew the distributor had to be replaced because something was going on with it and im not to familiar with breaking one down so i bought one for 45 bucks. Got it on and she fired up and i timed it (with the help of a couple others... the timing process is ridiculous you need 6 hands) but had an idle that would go from 600 to 1200 and back and forth.

I was so frustrated at this point i checked ebay and seriously almost clicked the buy it now on the motorcraft kit and distributor upgrade but i didn't. I went to the auto store and got a rebuild kit for the crappy carter and rebuilt it. Here's what i found....

The floats had previously been measured wrong and were almost stuck in the down position.... The throttle valves had also shifted (to a point where one side of them had ample light coming through) ... and some springs were set wrong under the dust cover.
So i adjusted the floats, loosened and adjusted the throttle valves and tightened them back up and built the rest of the carb from the ground up making sure everything was spotless and adjusted.

RESULTS: She runs like a beast! The air being sucked through the throttle valve had to be causing the variation in the idle and the floats were not supplying enough fuel at full throttle causing the cut out. Thanks for everyones input I probably would have givin up for a while if it was not for this forum.

Distributor $45... Carb Rebuild $15... Jeep that runs like it rolled off the floor, PRICELESS

Here's a pic of her so ya'll know what ya'll helped with!
jeep-yj.jpg  
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Unread 05-29-2012, 10:34 PM   #13
Karma
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HI,
That's great. Good for you. Can you tell us what was wrong with the old distributor?

Sparky
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Unread 05-29-2012, 11:27 PM   #14
Fernando
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What a beautiful Jeep! Glad you fixed it!
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Unread 05-29-2012, 11:31 PM   #15
AmmitOsiris
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Quote:
Originally Posted by Fernando
What a beautiful Jeep! Glad you fixed it!
Man I wish mine was that beautiful again
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