I replace my oil pressure sending unit in my truck and I am still getting a low reading

ELIK19

MEMBER
1994 CHEVROLET SILVERADO
5.7L
V8
4WD
AUTOMATIC
145,500 MILES

I replace my oil pressure sending unit in my truck and I am still getting a low reading at full operation temperature. I do have a oil leak that I am getting fix. On a cold start I have no smoke, ticking, knocking, or odd sounds even at full operation temperature. My check engine light is not on at all. My idle is low I run down near 500 and 600 rpm's. When the truck is in drive in park my oil pressure goes up and I get a good idle. Should I get my oil pump tested for a "real" pressure test kit and see if gauge is broken or what?

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

This issue could be due to a bad gauge. It a possibility of a bad pump or having blockage on the oil pump screen. However, when the oil pressure is low usually the engine will make noises as it is not getting oil properly.

First step would be to actually test the oil pressure, that way you will know for sure that it is either a gauge or the pump.
The oil pressure can be tested using a pressure test gauge and installing it to the oil pressure sensor location.
This vehicle should have minimum of 6 psi at 1,000 RPMs, 18 PSI at 2,000 RPMs, 24 PSI at 4,000 RPMs.

https://www.2carpros.com/articles/high-or-low-engine-oil-pressure

If the pressure is good, then it is likely a bad gauge. These gausses have stepper motor that controls them, those can go bad and provide incorrect reading.

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.

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