Oil Pressure - How high is too high?

[walshje]

Just recently bought a 91 Jimmy with 169K on the 350 in it. It was meticulously maintained since new, currently has synthetic 0W30 oil in it. Driving on the interstate at 55MPH the oil pressure gauge is pegged or very nearly pegged at 80PSI. At idle it is at about 40PSI.

I'm thinking that the gauge must be wrong, this thing can't truly be at 80 PSI? I guess I could install an aftermarket gauge as a sanity check, just wanted to be sure that this isn't normal for this generation of truck. For what it's worth, the previous owner told me that the PCV valve was replaced ~10K miles ago, haven't personally popped the hood to verify yet.

[maxwedge]

Get a external test gage on it first, pressure is too high, or at least high for that engine.

[j cAT]

Originally Posted by walshje

Just recently bought a 91 Jimmy with 169K on the 350 in it. It was meticulously maintained since new, currently has synthetic 0W30 oil in it. Driving on the interstate at 55MPH the oil pressure gauge is pegged or very nearly pegged at 80PSI. At idle it is at about 40PSI.

I'm thinking that the gauge must be wrong, this thing can't truly be at 80 PSI? I guess I could install an aftermarket gauge as a sanity check, just wanted to be sure that this isn't normal for this generation of truck. For what it's worth, the previous owner told me that the PCV valve was replaced ~10K miles ago, haven't personally popped the hood to verify yet.

the pressure indicator gets a current flow by the resistance of the oil sender...if the resistance is very high [open] you will get a 80psi reading..

because of the age / mileage,, I would check the wires and connector for corrosion and the sensor pins...then with the wire removed and the engine running measure the sensor resistance...as you vary the rpm..

if the engine runs good it most likely is the wires or sender not engine..but this should be tested ...


the resistance of sender no pressure is 0 ohms, at 80 psi 90 ohms....if you get 200 ohms then you know sender is defective ...if it does go to 90 ohms at a high idle like what you would see at 55mph then you must check this with a guage.