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razormedic911 05-21-2013 08:52 PM

something wrong with the wiring???
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????

KJL 07-22-2013 02:17 PM

I've had a similar situation and the problem that I discovered was on the rear driver side near the rear shock is where the main engine harness plugs into the fuel pump module harness. I discovered that "someone" had mess around with the wiring in the plug connector on the short length of wiring harness leading to the tank. they botched up the wiring (maybe the harness got hung up in the shock if they were off-roading it? not sure) so i ended up soldering the wires as best I could in the connector plug itself and then 3 years later just due to bouncing down the road the systems came back and left me stranded again. I've read on here that a possible fix is to cut the plugs and hard wire the four wires - just so you have enough slack so they don't break again. The other fix I read about was that you can buy the entire fuel pump module which is one piece and includes the harness and fuel pump - but i think that's about $300. I wanted to just buy the short piece of harness but it is unavailable. hope this helps.

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