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Incorrect Oil Pressure Reading

asymptonic

NAXJA Member
NAXJA Member
Location
Austin, Texas
Continuation of my thread about my new Jasper motor. Just got it back from the shop where they had read a hot idle oil pressure of 20psi with a mechanical gauge, while the dash gauge shows 9psi.


The sender has been replaced, and I finally bought my own mechanical gauge to double check their work (don't particularly like this shop, but they were one of two local shops that would work with Jasper and the other was even less reputable).


Lo and behold, it is indeed 20psi on my gauge. What are my next steps. Wiring near the sender looks new. I'll try and check the wiring to the ECU and dash, but I'm new to electrical. What would you do?
 
Start by cleaning up all the grounds, mainly the ones on the dipstick mounting bolt first.

Get rid of any Teflon tape on the oil pressure gauge threads.
 
Interesting, there is some teflon tape on the new gauge. What would be the effect of that beyond the presumably better seal? Ground issue?
 
It can effect the body/core temp readings but grounding is done thru the ECU sensor ground.
 
It can effect the body/core temp readings but grounding is done thru the ECU sensor ground.

The teflon? I thought the temp sensor was near the fuel rail.


In the same engine replacement I sprung for the max cool mopar radiator. After a ~1500 mile roadtrip which had had trouble in the last, hot, uphill segments on previous trips, temps looked remarkably stable at about 195 by the gauge with no overheats (two minor ones on previous trips). So the temp readings at least feel and seem right.
 
Spent yesterday cleaning up the grounds near the dipstick (G101) and the alternator which was the bigger problem (G103). Went from 1.4 ohms from the dipstick to battery to 0.6. But the gauge is still reading low. Will look at the block to firewall ground this weekend, but barring that, what should my next move be?
 
Since the sensor is grounded through the ECU, you could check that the ECU itself has good contact with the body. I use electrical grease on all my connections.
 
Since the sensor is grounded through the ECU, you could check that the ECU itself has good contact with the body. I use electrical grease on all my connections.


Will do. I also want to check the resistance at the sender and compare it to the resistance at the pin to the ecu connector. BTW, isn't dialectric grease non-conductive? Or is this some other electrical grease?
 
Story so far:


Sender Connector to ECU pin: 0.1ohm
ECU ground to battery neg: 0.2ohm
Power on voltage across sender: 5.1v
Still need to figure out how to test the sender ground itself, since its the 2 wire 98 style that grounds through the connection to the oil filter adapter.
Instrument cluster sweep test looks correct.

Nothing looking bad so far. Is there a way to test the sender itself?
 
Last edited:
Nope, it needs to be "conductive" grease(anti-ox)!
 
Just for closure, the issue did turn out to be the sender. I suspect that though they *said* they put a genuine Mopar sender in, it wasn't. I ordered my own and the Mopar one uses different thread sealant and has the part number stamped into it. The one from this shop didn't.


New sender accurately reflects the mechanical gauge.
 
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