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Unread 05-21-2013, 03:26 PM   #1
razormedic911
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1994 ZJ 
 
Join Date: Nov 2012
Location: Palm Bay, Florida
Posts: 16
short somewhere...someone please help!!

Ok, so let me start with a little background and what I've done so far. I've been having problems with my TJ for a while, mostly running rough. It seemed to top out at around 3000 rpms, regardless of gear, and for a while has had this annoyingly intermittent condition where if i drove around town for a while, it would be very difficult to start, sometimes taking 5 mins, sometimes 20 before it either killed the battery and required a jump, or would miraculously turn over like nothing had happened.

This was annoying, and though it prevented me from taking the TJ out to play, it was function-able driving to and fro to work...until last week. As I was driving down the road, i noticed that it was running increasingly rough, and that the voltmeter had suddenly dropped to zero. about a hundred feet down the road, the truck stalled and wouldn't refire...just click click clicked from the starter. I pushed it into a parking lot, and started troubleshooting. First off I replaced the battery as I had drained it completely several times recently due to the above mentioned starting difficulties. Also after researching here, It seemed that my problem could be the crank or cam sensors, so I replaced both of those. The result was a jeep that cranked, but ran like crap, and wouldn't idle without considerable effort wit the gas pedal.

Side note, it was during these recent troubles that I had been noticing a sweet spot about half throttle which was the only place the truck could make power, and this condition remained. When I first noticed this I tested the TPS as per the instructions in the service manual and it tested ok.

Anyway, I was able to limp it back to the house, and did more research. I had already shored up the ignition side, and was at the point that it had to be a sensor, the PCM or something on the fuel side. I got a pressure gauge,, and low and behold the fuel pump was only giving me 18 psi at the fuel rail Schroeder valve. well now we were cooking, I tracked down a replacement fuel pump, and set about swapping it out.

Now things get complicated. As I dropped the tank I found that the PO, in their infinite wisdom had apparently bypassed the FP relay, and hardwired the FP into the switched side of the electrical circuits- wirenutted wire going to chassis ground, and another wirenutted wire running up and inserted into the under dash fuse box. Given this ridiculousness, I tested the relay and wiring, and it appeared to be intact and functioning, with good grounds both at the fuel pump and at the relay in the PDC. given this, and not feeling completely comfy with a jerry-rigged FP circuit, I wired the FP back in using the factory harness, and viola! though I had already taken back the fuel pressure gauge to Autozone, on the first test drive not only did it run at idle, but I had power all the way through the power band, up to 4000 RPMs in all gears, and the truck ran better than it had in a long time. The only weird thing was that now after diving for a very short distance the voltmeter would bottom out, until I turned off the truck, and turned it back on, and it would again read in the middle of the gauge, and refire without hesitation this was Sunday. Yesterday we drove the Jeep all over, making several stops and multiple trips without a single hiccup.

today we had a heavy rain, and this afternoon when I took the TJ out, it cranked right up, but I noticed that there was a fluctuation in power to the stereo, and that my windshield wipers were running extremely slow. I got about a 1/2 mile up the road from the house and suddenly went from power to limited power to no power to stall, and truck wouldn't restart, just clicked.

I got a jump, and it started right up, but fizzled out several seconds after being put in gear. I climbed under the truck and changed the power to the fuel pump from the factory wire to the previously jerry-rigged power wire, but on re-jumping it did the same thing. It took 2 more jump-starts to get the truck turned around to face toward home, but eventually fizzled out again. o now I wait for my father-in-law to help tow the Jeep back to the house, and am left wondering were to begin looking for what i must assume is a wiring problem. Can anyone give me any guidance where to begin????

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Unread 05-21-2013, 07:17 PM   #2
Rubi4MyMrs
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2005 LJ Wrangler 
 
Join Date: Mar 2011
Location: Trails of, Nevada
Posts: 2,515
When all this happened today in the rain, was the volt gauge dropping or normal?

Put the FP wiring back through the relay. Whatever wire it was attached to is probably too small to operate whatever it is supposed to plus power the pump. That is probably overloading that wire & the pump is underpowered. Low voltage can also cause the pump to overheat. That could cause the pump to fail prematurely. Depending which fuse it is tapped into that might have caused other issues. Do you know which fuse it was tapped into?
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Unread 05-21-2013, 09:28 PM   #3
mukluk
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2000 TJ Wrangler 
 
Join Date: Oct 2010
Location: Clyde, Texas
Posts: 1,466
I'd put my bet on you have numerous bad/poor electrical connections. TJs are quite finicky about having a good reliable DC power source from the battery for the PCM, poor battery cable connections (at the battery and engine block/alternator/PDC ends) will result in "interesting" running and electrical system problems. What I would highly recommend is to thoroughly clean all the connections at both ends of both battery cables (couldn't hurt to ohm the cables as well to ensure they aren't degraded), have the alternator tested for proper output, repair the original factory wiring for the fuel pump and relay, and remove the jury-rigged wiring for the pump and relay.
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Unread 05-30-2013, 10:03 PM   #4
razormedic911
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1994 ZJ 
 
Join Date: Nov 2012
Location: Palm Bay, Florida
Posts: 16
***Update***

The problem apparently was a bad alternator.

After testing all the connections again involving the FP circuit, I swapped in a spare alternator that I had laying around, and deep charged the battery, and viola! It started right up first time, and stayed at 14 Volts, I ran it all over today, including a 10 mile trip up the interstate to work. It runs great, and didn't falter one bit. Starts every time, has power throughout the RPM band, and the voltmeter does not move. Incidentally, I also noticed my water temp is now staying way lower than before, a condition I'm assuming is the result of putting the proper tension on the serpentine belt, making the water pump turn more efficiently.

Now that everything seems to be working, I'm left to ponder. . .were these all unrelated coincidences, or did one problem beget the others???
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fuel pump , no start , short , wiring

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