95 JGC no oil pressure

[95jeepgc]

I have a 95 jeep grand cherokee. We lost oil pressure assumed the oil pump went out. We replaced the oil pump, we primed it too, and still no oil pressure. I need some help any ideas.

[DanB98TJ]

Did you check to see if there is oil pressure with a mechanical gauge, or are you relying on the factory gauge? If so, picking up a cheap mechanical unit will rule out any problems with the sending unit, gauge, or wiring.

Are you getting any oil circulating (pull the valve cover, prime the pump and watch to see if oil flows to the rocker arms)? Not sure if the 4.0 uses a driveshaft for the oil pump, or if it just engages the bottom of the distributor, but I'm assuming the drive on both ends was good?

Worn bearings can cause low oil pressure, but it sounds like it was a sudden drop in your case so I doubt that is the issue.

[JLemieux]

Originally posted by DanB98TJ
Did you check to see if there is oil pressure with a mechanical gauge, or are you relying on the factory gauge? If so, picking up a cheap mechanical unit will rule out any problems with the sending unit, gauge, or wiring.

I agree, this is the next step. If you can get a hold of a wiring diagram to find the correct wires, you can momentarily ground the signal wire from the sender to the gauge to see if it moves the gauge.
Should I assume that the oil filter was changed when you replaced the oil pump? I have seen oil filters that are so cheap that they don't have a bypass valve in the event the filter collapses or gets plugged. This results in little or no oil pressure.