oil pressure

[gilbertmonchat]

hello, i have some probleme with my oil pressure gauge, with the engine at normal temp. oil at normal level, no noise, nothing wrong but my gauge (oil pressure), drup to one or two line before 0 ,at idle 800rpm. and when i accelarate to 1800rpm the gauge come like normal at 275. Any ideas

[moondoggie]

Good Day!

The oil pressure switch/sender is notoriously unreliable in our trucks. You really can't trust the readings, unfortunately. The switch part seem to fail most often, causing the lift pump to not get power when running, which has it's own set of symptoms; the sender part also can give troubles like yours.

They're not horribly expensive, so maybe arbitrarily changing it out isn't a bad idea. If you're going to keep the truck for a few years, you'll probably need it eventually anyway.

What units does your oil pressure gauge read in? I'm used to PSI, but can convert most anything. I used to typically see ~ 20 PSI at idle, & 30 or so when running down the road (hot) (Sub & pickup both); lately my pickup has been running considerable higher, ~ 30 at idle & 40-45 PSI running down the road (hot). I suspect the oil pressure hasn't changed at all, just the sender; otherwise, my change (a year or so ago) to Synthetic Rotella 5W-40 has made the oil pressure go up, but I don't think so.

Blessings!

[gilbertmonchat]

if i understand, can be the oil pressure switch or only the gauge , but if it's oil pressure
switch, that change something on the good running of my engine? and where they is on engine?...............sorry for my english !!!!

[moondoggie]

Good Day!

There is one part, which I choose to call the oil pressure switch/sender. It's threaded into the back of the motor, on top, behind the intake manifold (kinda hard to get to). It serves two functions: 1) it provides a contact closure when the oil pressure is adequate (10 PSI? I don't remember), which powers the lift pump when the engine's running; 2) it provides a variable resistance to ground, which is the drive signal for the oil pressure gauge. Soooooo, there are three terminal in its connector: two that short when oil pressure is adequate (lift pump), one that has variable resistance to ground, proportional to oil pressure (gauge).

If you searched this forum for lift pump and oil pressure gauge, you'd probably get more info than you can handle about both functions of this part.

Blessings!