Oil pressure needle jumping

[daShadow]

Today while driving my 1999 Ranger 4.0l, the oil pressure needle started jumping between normal and zero. After a couple of minutes it would go to zero and the red Check Gauge light would come on, then back to jumping and then only zero. Stopped to check oil and full. The way the needle was jumping, there was no way the pressure could change that fast, although I do know it is not a real oil pressure mechanical tube pressure switch. So I'm guessing it is the sending unit. Will check tomorrow to see if it is throwing any codes. Any thoughts about this???

 

[rusty ol ranger]

My 97 460 did this then shortly after the mains started knocking.

But i doubt thats the case.

Its either the sender itself or the wire plug that goes on the sender loose.

 

[Dirtman]

The sending units are really just switches, they are just on or off and have zero or nothing for pressure but for some reason ford hooked them to a guage that makes them deceiving. It is most likely just a failing sending unit but it's not something I would let go just in case you are in fact losing oil pressure. Change out the sending unit asap and if the problem persists put a real pressure gauge on it and check the true oil pressure.

 

[RonD]

Yes, check the sender, its on drivers side of block just in front of the dipstick tube, you can see it thru drivers side wheel well or from underneath

Usually on the end of a hex shaped extension, seen here: https://www.justanswer.com/ford/1ie74-oil-pressure-reads-just-above-red-line-1991-ford.html

If you unplug its wire and then GROUND that wire, that will compete the circuit like the switch does
Turn on the key and oil gauge should show steady reading between 1/4 and 1/2
Start engine and see if gauge changes, may go up a tad with higher voltage from alternator, but not jump around, if it does then wire or gauge is the issue.

If wire and gauge check out OK, then remove the sender
Disconnect coil pack's 4 wire connector for a No Start, disable spark
Have a towel or pan under senders open port
Crank engine so any old oil and debris in that extension gets pushed out by oil pressure
Install new sender


A dirty oil filter can cause loss of oil pressure
The 4.0l OHV engine will make "ticking" noises from lifters/rockers if oil pressure actually drops below 5psi, since you didn't mention any noise I don't think oil pressure was actually low