99 Jeep Oil Pressure

My oil pressure gauge is pegged to its highest PSI. A friend says it is the oil pressure sensor shorting out.

Does that sound correct?

Pull the connector off of the sender. If the gauge now reads zero, your friend is correct.

Entirely poss. your friend is right; but; 4.0L, or 4.7L? You could diagnose this problem for 29.99 (4.0 sender @ Pep Boys; 53.00 for 4.7L sender @ Advance Auto here where I live.) Replace sender (just to rear of oil filter on RH side of engine on 4.0; not sure on 4.7L.) If gauge reading drops; culprit was old sender. If you remove sender wire and ground it and gauge pegs; or if you remove it and don’t ground

it and gauge goes to zero, sender could still be OK cuz you might actually have extreme oil pressure. How? Bad pressure relief valve in oil pump, allowing pump to develope too much pressure. This could push oil past piston rings into combustion chamber via the cyclic squirt of oil from rotating crankshaft. (All this ain’t likely but…) You may need an oil sender socket- (mine was under 10.00)- for 4.0L

sender- not sure about 4.7L. Obtain from parts place that sells tools. The best- if you know someone w/oil pressure gauge- just unscrew sender and install gauge where sender was- wish I had specs. Anything over 10 PSI is OK (warmed up engine @ idle!). But you’d like to see more. I will post back W/specs 2:45PM EST Sun. KS

You hope so. Too high is not any better than too low.

What Karl sez is exactly right if the gauge pegs only when the engine is running.

If it pegs with the key on engine off, then look for a short in the sender or the wire to it.

Ouch 53 bucks for a sending unit. I’ve never spent more then 8 bucks for one on my Fords.

I suppose these days that the mechanical sender has been replaced by an electronic oil pressure monitoring module. Or some such nonsense.

Right you are, 87 Ranger. Key on, no wires disconnected or anything, if gauge pegs- short in sender circuit; most likely sender itself. I hadn’t thought of that. Also if you disconnect wire from sender, ground it- key on- and it doesn’t peg gauge, could be gauge but now go to pressure test I would say. More than one way to skin a cat, though.

You asked about an oil sender on a 99 jeep. Since it probably wouldn’t matter which model you have since sender is on engine, then it would have been nice if you’d given engine size at least so we wouldn’t have to play “internet tag”, but I still want to help you! Hope you’re still checking this website. All these tests are done w/engine completely warmed up except where indicated: 4.0L: @600 rpm: at least 13 psi. @1600rpm or more:37-75 psi (no more than 75) Sender location is above oil filter on rh side of engine.

2.5L: same as 4.0 'cept extra measurement- @800rpm 25-35psi

4-7L: @idle but NOT WARMED UP: at least 4 psi. @3000 rpm: 25-80psi, not over 80.