Hello, I have a 98 Cherokee 4.0 sport and I've been having oil pressure issues. I have a problem where the oil pressure will be anywhere between 15-50 psi, and it makes no difference whether the oil is cold or hot, or if the rpm's are high or low. Sometimes I will be driving and the pressure is 50, then I look at the gauge again and its down to 15 or lower. Lately the pressure is usually 13, even at higher rpm's, however just recently the pressure was 0 for a few seconds when I started it.

So I changed the oil pump with a new aftermarket unit. Now when I start it up, I get no oil pressure at all. I'm scared to even try to start it again! Help please!

 

So I am assuming you do have oil in the engine but maybe you have a seal problem

 

Which seal do you mean? I have some skill with a wrench, but very little experience with automotive. This oil pump is the biggest job I've tackled on a passenger vehicle.

edit: I put a new filter and new oil on before I cranked it over.

 

You might want to check the oil pressure switch that's located next to the oil filter. My pressure was maxed out all the time and then dropped to zero. New switch, 2 minutes later and everything is good.

 

When my oil was low my pressure varied also, but when I changed my rear main seal my oil pan gasket was offest (so I had a leak) and the gauge was still awry

 

Thanks, I'll take a look at my oil pressure switch.

I hope I didn't just replace my pump for nothing, and then crater my engine because of it.

 

My wife was panicked one day when the oil pressure was fluctuating wildly. Truthfully, I'm surprised that she even noticed. It turned out to the sending unit close to the oil filter.

My pressure has been showing lower than I would like, and I want to get a mechanical gauge hooked up to see if my electric gauge and sending unit are accurate. I changed the oil and filter on Saturday and pressure has increased at least 5psi. I used the Mobil 1 filter of the same size as Motorcraft FL1A or Fram PH8A. Its a larger, likely double volume filter.

 

Picked up a sending unit, $40 later, still no oil pressure and my engine is making a brand new noise! Tomorrow I'm taking off the oil pan again.