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Unread 03-21-2014, 01:56 PM   #1
jpatyj90
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1990 YJ Wrangler 
 
Join Date: Mar 2014
Location: south fallsburg, ny
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need help with my 90 yj

My 90 YJ was starting but stalling as soon as I let go of the key. I had it towed to a local garage to see if they could figure out why. They replaced the fuel pump and then told me I needed a carb I couldn't afford what they wanted to replace the weber 32/36 that was on there so I replaced it myself. Just got it done and am now right back where I started. It starts but wont stay running. I would appreciate any help I can get.

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Unread 03-21-2014, 02:03 PM   #2
Mark05059
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ignition control module under the washer bottle on the passenger side.
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Unread 03-21-2014, 02:05 PM   #3
jbolty
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I really hate mechanics who just throw parts at problems. At least you didn't have to pay those jokers labor.


I would start by testing the circuits at the ignition switch.
ign1.gif

ign2.gif

ign3.gif

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Unread 03-21-2014, 06:57 PM   #4
Old4X
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Put the ign switch in the run position (for no longer than 30 sec) and see if you have power at the + terminal of the coil. It will be under 12 volts as the ignition resistor wire drops voltage when running to around 8 volts or so.

Turn ign off.

Do this again and see if wire # 11 (at the ICM) has power in run. If it does, look at the clip on connector on the coil and check for voltage.

If voltage at the ICM but none at the coil in run, your resistor wire is bad.
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Unread 03-21-2014, 10:00 PM   #5
plym49
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I know that issues like this are upsetting and that it is hard sometimes to keep a calm mind when things are happening.

For future reference, apply the sniff test:

The problem is associated with the movement of an electrical switch - therefore the most likely cause is something electrical. You probably got that far on your own before your rig was towed.

But now these porkheads are telling you it is a fuel problem.

Fuel pump? How could your mechanical fuel pump know whether the ignition key is in the start or run position? Obviously, it can't. Also, you have a carb. Carbs have fuel bowls. There is a volume of fuel in the bowl. How could the fuel bowl magically and instantly empty and refill as you move the ignition key? Obviously it can't, so right away we know that the fuel pump is fine.

On to the carb. The same logic applies. How would your carb know if the key was in start or run? And if it did, does anything inside the carb change from start to run? It would not even with the stock Carter feedback carburetor; it certainly does not with your aftermarket carb. So, again, you know that the carb is not the problem.

The ignition troubleshooting advice is correct. Follow that and you can fix this yourself.

Moral of the story: when faced with a mechanical problem, use logic to rule in what it could be and to rule out what is ridiculous to even consider. You will save yourself mucho money as most mechanics like to throw parts at jobs they like to do (replacing fuel pump or carb is a lot easier and more profitable than chasing an electrical problem) and jobs with the highest margin.
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Unread 03-22-2014, 03:42 PM   #6
eljibaro127
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My 88 4.2 had the same prob turned out to be the ignition switch its like 20 bucks at autozone and has lifetime warranty.
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Unread 03-30-2014, 07:48 AM   #7
jpatyj90
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Quote:
Originally Posted by Old4X View Post
Put the ign switch in the run position (for no longer than 30 sec) and see if you have power at the + terminal of the coil. It will be under 12 volts as the ignition resistor wire drops voltage when running to around 8 volts or so.

Turn ign off.

Do this again and see if wire # 11 (at the ICM) has power in run. If it does, look at the clip on connector on the coil and check for voltage.

If voltage at the ICM but none at the coil in run, your resistor wire is bad.
if I have 12 volts at the coil with the key in run position what if anything does this eliminate ?
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Unread 03-30-2014, 08:34 AM   #8
jpatyj90
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if i have 12 volts at the coil when the key is in run position does this eliminate the ignition control module and the wire between them , and is there a fusible link that could be a problem ?
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Unread 03-30-2014, 03:24 PM   #9
Old4X
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Quote:
Originally Posted by jpatyj90 View Post
if I have 12 volts at the coil with the key in run position what if anything does this eliminate ?
It says your ignition switch is fine (should be 8 or 9, not 12 volts, though).
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Unread 03-30-2014, 03:29 PM   #10
Old4X
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Quote:
Originally Posted by jpatyj90 View Post
if i have 12 volts at the coil when the key is in run position does this eliminate the ignition control module and the wire between them , and is there a fusible link that could be a problem ?
No, it does not eliminate the ICM.

The ICM breaks the ground to the "tach" post on your coil and causes it to dump the energy into the coil wire leading to the distributor.

If it is firing in "start" and quits in "run" , that tends to point to a bad wire betwen the ICM and the ignition coil. The wirind diagram above shows it.

IIRC, it goes through the start relay on the firewall under the battery
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Unread 03-31-2014, 06:24 AM   #11
medic-11
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Follow this advice. Its really not that hard to troubleshoot this. If you need more help we are here, if your not sure about something take some pictures and post them up it'll make helping you (and you understanding everything) easier.
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Unread 03-31-2014, 08:41 AM   #12
Que89YJ
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You have a webber on it so has the nutter bypass mod been done to it?
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Unread 03-31-2014, 02:12 PM   #13
jpatyj90
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Quote:
Originally Posted by Que89YJ View Post
You have a webber on it so has the nutter bypass mod been done to it?
I'm not sure what that is. The weber was on it when I got it though two years ago I'm guessing it was done.
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Unread 03-31-2014, 03:07 PM   #14
Que89YJ
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where the switched ignition feed to the coil it take a jumper wire directly from battery positive to it and see if it starts and runs.
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Unread 03-31-2014, 05:05 PM   #15
jpatyj90
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Quote:
Originally Posted by medic-11 View Post
Follow this advice. Its really not that hard to troubleshoot this. If you need more help we are here, if your not sure about something take some pictures and post them up it'll make helping you (and you understanding everything) easier.
I tested for voltage at (my "newly installed" starter relay) with the key in run position (on my "new ignition module"). It had 12.85 at the main terminal from the battery. In addition to the heavy ga. wire from the battery there are three additional wires that run to fusible links and disappear into the wiring harness on that terminal. I also tested for voltage at three of the four blade type terminals on the relay. there was 12.85 at the Fuel pump ballast resister? terminal (far left in pic 1) it is green/wht stripe. nothing at the starter solenoid term.(center of clip) also green with wht. stripe and nothing at the ignition terminal the solid green wire on right of clip.(top to bottom when attached to firewall ) The other the ground terminal? has a smaller gauge black with wht. stripe wire. I then tested for voltage at the ICM(pic 2 ) I unplugged it and and got 5.01 on the lime green wire that goes to the orange wire on the ICM side of the plug. 12.70 at the green with white stripe ( goes to solid green on ICM side of plug ) nothing on the black (also black on ICM side ) there is nothing going into the plug that goes into the purple wire at the ICM side. On the other plug that has the two heavier gauge wires there was 12.70 on the yellow wire ( red on the Icm side ) and nothing on the green wire ( white on the ICM side of plug ). Sorry could not upload photos it said the forum only allows 540 kb for this file type (jpeg ) and the photos are 1.8 mb
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