I am replacing my oil sending unit's connector on my '99 XJ. Downside is that the wires from the new connector are green, orange and black and they don't correspond to the three wires from the wiring harness. The sending unit worked fine until I broke the old connector (which I already tossed). I spliced the old and new wires (3 of them) together in various combinations. In one combination I got a constant reading at the 10 mark. In another, the engine kills. In another, the one I'm leaving it at, I get the constant of 50. Is it possible I messed up the sending unit by trying the different combinations? When it worked, my oil pressure was like 30 at idle and 50 when travelling.

 

According to my 2000 FSM, looking into the plug with the lock on top, the terminals are numbered from right to left. #1 is 5v supply, violet with orange tracer, #2 is sensor signal, grey with yellow tracer, and #3 is sensor ground, brown with yellow tracer.

Yes, it's possible you shorted the signal wire by applying 5v directly to it. The way it works is 5 volts energizes the coil and pressure changes the voltage coming out of the center tap, similar to how a volume control works in a radio. The one on my WJ 4.0 broke in half when I changed it and it had a chip or crystal inside it. I'm assuming it's a piezoelectric crystal that changes conductivity when pressure is applied. It's definitely not like the old diaphragm and resistor type like the old ones were. Those were only one wire.

 

Thanks much Dave! I will get back at it come daylight. I'll have someone looking over my shoulder as I compare your wiring notes with what I have. I'm red/green color-blind so I don't see violet (blue to me) and brown (green to me), so a person that sees colors normally looking over my shoulder will help.

 

Ouch! Now that's a handicap! I sometimes have to clean the wires with cleaner to be sure of the colors myself.

Here's something you might enjoy. My passengers tail light wasn't working nearly at all, so I took off the inside panel to check the wiring. I found the harness connector was green with corrosion with a couple of melted terminals. I just cut both sides of the connector out and joined all the wires by matching color codes. The light was working weirdly and not properly at all. Luckily I hadn't thrown the connector away and looked closely at it. Some of the wires changed color code across the connector and used the same colors for different circuits! WTF? I had to find the hot tail light wire and use it to probe and mark what all the others did and connect them. The only one that was right was the black ground. What should have been a simple repair took 2 days because it was 10*F outside and my fingers got numb quickly, plus it was too cold to solder. I had to go buy self soldering butt connectors and use a pocket torch to shrink them. Everybody thinks I smoke crack because I bought that nice little butane torch! I had trouble even with that because below 32*F, butane doesn't evaporate.