I have a '98 xj with 168k miles on it . my problem is the oil pressure fluctuates at constant rpm (example it varies from 25 to 40 psi @ 2500 rpm and from 5 to 20psi @ idle). The sending unit has been changed but problen still exist. Could the pump be bad?

 

Sure could be. I'd get a mechanical gauge to test it. You can rent them free at a lot of auto parts stores, and that will tell you if you have a real problem with pressure or a problem with sender/gauge in your Jeep.

 

I agree. If you want to truly verify, rent a mechanical gauge from a parts store.

Or if it's the original sending unit, you could also just replace it. It's a very common failure. I recommend a genuine Mopar oil pressure sending unit for the best reliability/accuracy/mating with your factory gauge.