I have a 97 Cherokee sport with the 4.0. Whenever I bought it last June the guy said the oil pressure sending unit was bad. I replaced it after I bought it and no fix. The gauge will usually start around the middle of the gauge when I start and as I start driving it will drop to zero. It randomly moves back up to 40ish.

Any ideas on what could be causing the issue? Could the gauge just be bad?

 

Yes, the gauge can go bad. The wiring between it and the sender unit can go bad...and the sender itself can go bad. (New replacements have been known to be bad right out of the box too...)

With the key on but engine not running, disconnect the wire from the sender. This should peg your gauge to full pressure reading. Next, ground that wire to something in the bay and check the gauge. It should read zero or close.

If it does that, the sender is bad. If not, the wiring and/or the gauge is bad.

 

Thanks a lot! I may try that tomorrow. I was kind of figuring the gauge may be bad but that should show me more of what the issue is.