What to check next for oil pressure?

fourmustangs

fourmustangs

TJ Enthusiast
Joined
Apr 10, 2017
Messages
280
Location
Houston, TX, United States
I'm having the oil pressure gauge drop to "zero" after warmup. it stays up high when cold and when driving it stays up high.

I just replaced the one wire oil pressure sensor, nothing changed...low at idle after warm-up.

I had someone check pressure, said it stayed at 20psi for an hour.. at idle.

what would next check be to keep gauge from setting off check gauges light.

no idle issues, very smooth. 135k miles

2005 4.0 Auto
 
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I got 180K miles out of my oil pump before it did the same thing. Fine around town but run on the highway, get everything warmed up, stop at a light, zero pressure, alarms and warning lights. Touch the gas pedal and the alarm went off, pressure camr back up.

The dealer told me $1000 for a new pump. I found a remanufactured engine so new pump, no RMS leak, no leaky valve cover plus a tight engine with full compression and a 7 year warranty for $1800. Best choice ever, I now have 220K miles on the TJ, runs like new.
 
I think that the gauge on the instrument cluster is a go no-go gauge, if pressure is above ~ 6psi the gauge will be just above the 1/2 way point and it looks like you do have pressure.
You should run an Instrument Cluster self test to make sure the gauge itself is good, and if it is you might just need to clean the two connections behind the instrument cluster.
 
I will prob try that... during winter the gauge stayed steady then it got warmer and started doing this... since it went up with rpm didnt think it would be wiring, or plugs behind cluster but again its a jeep
 
The factory oil pressure gauge is about as useless as they come. I literally wouldn't pay any attention to it at all for any form of accuracy. You need an external gauge for that.
 
fourmustangs said:
what oil weight should I use, about to do oil change. im in Texas so will be 100 degrees soon
Click to expand...
I use 10w30 blend

Oil viscosity.JPG
 
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10/30 conventional might solve yer problems.... for awhile. If you are getting the zero pressure, red lights and audio alarm.... it will be a temporary solution. But as said, synthetics only advantage is remaining fluid at 40 below zero. It has zero advantage in more temperate climates. Sort of like buying premium gas for a TJ.
 
I had an engine that was about 5 psi at idle, put in some STP and 15w40, it went up to about 12psi. Temporary fix...
 
Putting regular oil will not help his oil problem, if he truly has only 5psi at idle. He could hear his lifters click, and his hearing clearances are probably excessive and you will need a thickening get the pressure up. One major bitch about doing it this method, is it is hard on the odpa and not a long term fix for a worn out motor. I have seen straight 50 weight ran in engines with low oil pressure.
 
I have 20psi...jeep gauge is like 5psi
Click to expand...

Sounds like you definitely have an electrical type problem, the one wire sensor is a go no-go gauge, it functions like a light except with a gauge. the gauge is either at 0 or just above half way when functioning correctly.
Have you run the Instrument Cluster test yet, that will help you in determining if the gauge itself is faulty and/or if you are having communication errors between the cluster and PCM (which is how the oil gauge gets its on or off signal). I do not think changing the oil will do much for the gauge issue.
 
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