1989MichJeep

Hey, y'all. I have a problem. I recently acquired an 89' jeep Cherokee 4.0l Inline 6. It hasn't had the best oil pressure the whole time I've owned it, but today it went from the usual 25lbs, to between pegged out and 10 lbs. the engine doesn't have a knock. the pressure doesn't change between applied throttle and an idle. It has 225xxx miles on it. Any ideas fellas?

toasterknight

Have you verified with a mechanical gauge? The factory sensor or gauge could be having issues.

vonsazkin

I am having a similar issue right now with my 2000 Cherokee Sport 4.0L. Could be oil pump, could be the oil pressure sender or could be something else. I changed the oil pressure sender today but the pressure is still between 20-25 at hwy driving (used to be 40-50) and 10 at idle. I am wondering if the oil pump is in need to replacement.

toasterknight

It could also be worn main bearings. Have you ever done an oil analysis to see if you have coolant in the oil from a cracked head since you have a 2000.

1989MichJeep

I've yet too. That's the next step.

cruiser54

Absolutely. VERIFY.

thatXJguy

Verify with the mechanical gauge. If it's the same, you've got a bearing issue. If it's not, you've got a sensor issue.

cruiser54

Okay, we've been hijacked here......

1989MichJeep: What you describe with the oil pressure reading lower than normal and then pegging, is classic oil pressure sending unit failure.

extrashaky

Harbor Freight sells a pretty decent mechanical oil gauge for around $25, even less if you find one of their 20% off coupons. It has a six foot hose so you can drape it over and watch it from the driver's seat.

Also, if the pressure is sometimes pegging, check the wiring going into the oil pressure sender. Mine was pegging, and when I went looking for the cause I found that most of the insulation was gone off the wires all the way up to the wiring harness. I had to unwrap the wiring harness to get into good wire to splice into.

bigbadon

^^^x2^^^