engrboy5

Ok, before I get blasted here...let me state up front that I've done thorough searches, and can't find anyone (here or elsewhere) with this problem...

So I replaced the oil pressure sender on the Cherokee (has 163k mi) with a NAPA part because I was getting readings of 8 to 10 psi at hot idle. I really didn't think this would fix the low pressure problem, but was hopeful, because of the reported problems with the sending units, plus I get no knocking, ticking, etc. noises from the engine.

The new NAPA part gave the same readings. 8 to 10 psi at hot idle. Took it back and exchanged it for a NAPA/Echlin part...supposedly a higher grade part. At this point I also checked the pressure with a mechanical gauge. Got 31 psi at hot idle...that was a relief!

Installed the NAPA/Echlin part and it reads just like the other NAPA one, 8 to 10 psi at hot idle. So I get to thinking maybe I had a bad mechanical gauge. Tried another, different mech gauge. It confirms the reading of the first mech gauge...~30 psi hot. So I figured it must be the NAPA sending units and bought a new OEM sending unit. Installed it today, and it reads exactly the same as the two NAPA units. I also ran the diagnostic test on the gauge cluster, and it does what its supposed to per the FSM...

So I'm convinced the actual pressure is around 30 psi...per the mech gauges. The gauge cluster is OK per the diagnostic test. I think probably all three sending units were good...they all displayed the exact same behavior. Which means somehow the sending unit signal/voltage out is being disrupted before it gets to the gauge cluster itself. Right?

Could this be a bad ground somewhere? Any one have any other ideas? What should I do from this point??

Thanks in advance...
James

RTorrez1

I would check the wire that goes to the sending unit to make sure that it is in good shape also check the connector the plugs to the sending unit. The only other thing that I can think is maybe the hole the the sending unit screws into is obstructed. But really not to sure if that would be the problem since you are getting a good reading with the mechanical gauge but it's woth a look.

peep

I really want to trust Napa and the Echlin brand parts.
However I have had two Echlin TPS and an IAC fail me. I'm on the third Echlin TPS (Napa was good to exchange them without charge). I'm running the OEM IAC pirated off my Comanche project, and it has 200K+km on it!
I really want the Napa parts to be good as they are good folk, very helpful in locating and getting the parts. However for electrical components I think I will have to go OEM next. Just the dealer service is not open Saturdays, closed evenings by the time I get off work, and is hesitant / reluctant in setting the parts out for me to pick up from the sales group. Napa is kicking the dealers butt in customer service.
Tough to find suppliers providing the whole package.
As a note, watch your oil sending units for any weeping. I've had couple fail over the years and the oil pass right thru the sender and leaking out the connector side.