mamm7215

Just curious, what should the oil pressure read at idle. Mine's about 1/8 inch below half. Goes up ok when revved, just curious.

RustyJC

Yep, that's about what mine runs at idle when fully warmed up - with Delo 400 15W-40. Just a smidge under the 40 PSIG mark on the gauge. (As a note of interest, it's almost exactly where my wife's 5.9L Durango runs at hot idle, too.)

Rusty

wannadiesel

The gauge is a "virtual" unit, the computer will show a normal reading unless the sender says there's no oil pressure.

Gear Poet

wannadiesel -- that's interesting -- are you saying that the sender is an "on-off" unit -- either there's pressure or there's not -- and the fluctuations on my gauge are bogus? I hadn't heard that before.

Just need clarification.

wannadiesel

The sender sends analog info to the computer, the computer just ignores it. As long as the signal is above the minimum "safe" level, the computer calculates gauge position based on engine RPM. This was done in mid '01, apparently in response to customer concerns about what oil pressure readings were normal. Now they always read normal unless the sensor's bad or there's no pressure. There was a reflash for older 24 valves.

zulusafari

Crud. Now I need an oil pressure guage, too.

Gear Poet

And the computer also calculates based on oil temperature? Which means there's an oil temperature sensor, as well?

Because when the engine is cold, the gauge registers much higher oil pressure until it warms up. And when the engine is hot after a long run pulling a trailer, the gauge registers slightly lower.

Or is the system "rigged" somehow to show temperature fluctuations?

RustyJC

There was a reflash that dummied up the gauge as a fix to the "zero oil pressure" problem. My truck hasn't had it - it shows at the high end of the operating band when at a cold idle, then slightly below 40 PSIG at a hot idle. Highway oil pressure varies with oil temperature as well. If this is a computer game (and I don't believe it is), someone certainly went to a lot of trouble to make the gauge read like it should.

Rusty

J BODY

The Cummins "sending unit" is actually an "on/off" switch. The gauge has been programmed to make you happy.

DaNuGuy

Them dirty little buggers.

MK4288

well thanks guys now i am gonna be buggin about this now! sometimes its just better to be clueless! i don;t think there should be a problem your computer is programed to show if there is a problem with oil pressure right? besides if you didn't know about an oil leak on your way to work you will by the time you get there its a real bummer trust me!

jrs_dodge_diesel

My old Ford F150 had the dummy guage. The oil pressure sender was just a switch, anything over 7 PSI closed the switch. The guage was rigged too. Since it got 12 volts there was a resistor inline with the guage so the needle would move to one spot and look normal.

My 01' reads like a true guage though. 40 PSI at warm idle, and it varies with the RPM.

Gear Poet

My thoughts exactly. The gauge in my truck -- same year and model as yours -- behaves in exactly the same way. If it's a programming charade, it's extremely sophisticated.

It may be that the program allows the gauge to accurately indicate pressure down to a certain spot on the dial -- say 40 PSIG -- and then does not allow the gauge to drop any further unless "real" pressure drops below the threshold.