Excessive Oil Pressure

[Manche757]

89 MJ 4.0, 91K miles.  This morning while driving about 65 I noticed the oil pressure gauge was at 80, the top reading.  At first I thought maybe the gauge was faulty, but the needle fell back easily as I slowed down.  About 30 at idle.  I googled and found that oil pressure of 80 or above can be damaging.  Changing gauge readings suggest oil is flowing so not a faulty sending unit.  Possible broken pressure relief value?   

[AZJeff]

Have you confirmed the oil pressure by using a mechanical guage?  This is the first step, because oil pressure senders are known to go bad relatively often.

[Minuit]

 

If the sender is not a recent Mopar replacement, it is a potential suspect. If it's any aftermarket brand, it is suspect regardless of age, although my experience has been that the aftermarket temperature sensors are much more garbage than the oil pressure sensors.

 

The oil pressure gauge is quite accurate when the connections are clean and it is used with a Mopar sender.

 

I'd investigate the sensor way before worrying about the oil pump.

[Manche757]

1 hour ago, AZJeff said:

Have you confirmed the oil pressure by using a mechanical guage?  This is the first step, because oil pressure senders are known to go bad relatively often.

 

I have just noticed it and have not done anything about it.  The sender should be removed and a mechanical gauge attached there?

 

28 minutes ago, Minuit said:

 

The oil pressure gauge is quite accurate when the connections are clean and it is used with a Mopar sender.

 

I have had the MJ for 4 years. Problem not previously noticed. As far as I know, the parts are original to the truck

[Minuit]

Yes, the gauge comes with a set of adapters, and one of those will fit in place of the gauge sender. Compare the reading on the gauge with the reading on the dash. If they don't agree within a few PSI, you've got a problem with the gauge, the sensor, or the wiring in between.

 

You may be able to rent the gauge from a parts store.

 

Quick test of the gauge and wiring: With the ignition on, unplug the sender. The gauge should read the maximum reading. Now touch the wire that went to the sender to ground. The gauge should read 0 PSI.

 

 

[rokinn]

In the event you determine you need a new sender.

 

https://www.amazon.com/Mopar-W0133-1941653-MPR-Oil-Pressure-Sender/dp/B008ESZ5GO/ref=sr_1_4?dchild=1&keywords=oil+pressure+sender&pd_rd_r=ada2f841-6143-4137-9ee5-2bd35f25f91d&pd_rd_w=iMaYr&pd_rd_wg=bUBBI&pf_rd_p=77b3265a-64e6-4f39-8333-9b68451dda4b&pf_rd_r=G4T1MZCNC2B0X0GB18MK&pid=C17m4P4&qid=1598555757&sr=1-4&vehicle=1990-42-348-20-75-31-8-7-3363-244-8-2-19-137-&vehicleName=1990+Jeep+Comanche#customerReviews

[cruiser54]

1 hour ago, Minuit said:

Yes, the gauge comes with a set of adapters, and one of those will fit in place of the gauge sender. Compare the reading on the gauge with the reading on the dash. If they don't agree within a few PSI, you've got a problem with the gauge, the sensor, or the wiring in between.

 

You may be able to rent the gauge from a parts store.

 

Quick test of the gauge and wiring: With the ignition on, unplug the sender. The gauge should read the maximum reading. Now touch the wire that went to the sender to ground. The gauge should read 0 PSI.