There could be air in the line. You need to bleed it dry. Possible way turn on engine with no oil cap wait until oil spills out then quickly put the cap on it works for 2 stroke boats and I believe cars as well. This could be dangerous so I sugguest get a mechanic to do it. Also 98 cherokee's are well known for heaps of electrical and oil/engine faults in some incedents engine have caught on fire from no/low oil pressure and also overheating engines sell the car before you loose any money on fixing it. Im not against them as they had great sounding powerful engines and good offroad ability. Recently a 2008 grand cherokee caught on fire the owner a 25yr woman only just made it out alive 2nd degree burns.
