I bought the Jeep with a nonworking gauge and tried to replace it with an OEM Mopar oil pressure sending unit, but it did not fix the problem.
On startup the gauge shoots to beyond 80 and doesn't move an inch.
I would love to fix this, but I don't know how to diagnose and test what area of the system went wrong, whether it be the sending unit, wiring, or gauge.
I would also like to note that the plug for the sending unit only has one wire. I don't know if that is normal.
Let me know what you think, any help would be greatly appreciated! Thanks!

 

I've gone through a couple of Mopar sending units in the past couple of months. When they crap the bed they peg out to 80. They're under warranty so take it back and get a new one. With the unit removed try turning the key forward but don't start it and see what the gauge reads, it should stay at 0. Also, I'm pretty sure there's more than one wire.

 

Let me know about that wire. Mine is a 1996 btw. I'll remove the unit and key it and tell you what happens.

 

I pulled the plug and keyed it. Gauge still shoots past 80. If there is supposed to be two wires, how do I fix it?

 

get a second sensor.

 

Mine has one wire from the sensor.

Use a test lead with an alligator clip at each end, clip to sensor wire, clip to ground at battery. Gauge should read 0.


Did you use tape on the threads of the sensor? Sensor needs to be grounded. I use thread sealer only on the top of the threads, IOWs the lower portion of the threads are metal to metal at the block.

 

I've done that already. The unit that came with it, and the Mopar unit I bought to replace both did the same thing.. shot the gauge beyond 80.

 

I read something like last year but haven't found it again. If there is a short in the wiring to the sender it'll either read max or zero. If there is an open in the circuit it will read opposite, either max or zero. Just don't remember which is which. My gauge won't move from zero. Once in a while it'll jump or move a little. I think it means there's a short somewhere. Haven't had the ambition to dive into the harness yet to figure it out. I also read that if the gauge works during the test cycle it should be fine.