92 4.0L YJ Ignition Problem? (I think???) - Jeep Wrangler Forum
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Old 10-22-2011, 02:39 AM   #1
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Location: Oceanside, CA
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Unhappy 92 4.0L YJ Ignition Problem? (I think???)

I have a 92 4.0L YJ that has totally baffled me. Well about 4 days ago I lost all fuel pressure to the fuel rail. So I dropped the tank and I found out that the PO had bent the skid plate, deforming the gas tank. So his solution was to get a new sending unit and bend it at a 45 degree angle so that the pickup screen was touching the top of the tank. And in doing so the bracing on the sending unit cut the rubber fuel hose coming from the fuel pump. So I fixed the hose, skid plate, and sending unit and everything was good for about an hour. Then HELL started.

So an hour later I have fuel but now I have no spark. I have 12v going into the coil but nothing coming out. So being the genius that I am I replaced the coil, rotor, cap, spark plug wires, spark plugs, and throttle position sensor. After all this still no spark, so I pulled every fuse/relay in the block next to the battery and noticed that that they were corroded. So I cleaned all of them then replaced them, STILL no spark. After a dozen or more attempts to start I magically have spark.

Now 4 days later I magically have no spark or fuel when I come to a red light. I can hear the fuel pump when I first turn on the key. Any ideas guys?

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Old 10-22-2011, 03:12 PM   #2
Join Date: Jan 2011
Posts: 94
I had a similar problem, where my YJ would crank and crank, fuel pressure in the rail and no spark. I did the same things, spark plugs, wires, rotor, cap... and no luck. Turned out to be the computer. The thing that did the trick to help me figure it out was buying one of the handheld devices that Actron sells which lets you see the error codes in the computer (you can also do this with the key and count the flashes of the check engine light, and while that does work, it's a pain in the butt). If your computer is dead, the only fix is to swap it for another. I'm stripping computers out of compatible YJs (mine is a '91, currently running a '94 computer and everything works fine so from experience '91 through '94 interchange) and building a stockpile for the next time the darn thing dies.

Anyway, purchasing that handheld has saved me a lot of headache the second time the computer died. Might be worth a shot as you've exhausted the logical problems.


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Old 10-23-2011, 10:56 AM   #3
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Is there any way to check if the computer is bad?
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Old 10-27-2011, 03:31 AM   #4
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This just perplexes me.
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Old 10-27-2011, 03:33 AM   #5
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Oh and does the Actron tell you anything more than just counting the check engine light does?
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fuel pressure , ignition , yj 4.0

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