Hello all,

I own a 1991 22R Carb' manual 4Runner. It's a unique rig since it was originally intended to the UAE market and was brought to Israel by its first owner who was a diplomat. It has a second generation body, SR5 trim, IFS and leaf sprung at the rear much like the first generation. Its my daily driver and desert tourer.

On my way back home from work the other day, I suddenly notice the oil pressure gauge going dead. I might have imagined it, but I think I saw the needle climbing to the high briefly just before it went dead.
After I got home I first checked if the sender unit was connected. It was.
I replaced the sender unit with a mechanical gauge and found that the oil pressure is within manufacturer spec'.
According to the manual the resistance of the gauge should be about 25ohms, I got 27.
As the manual instructs, I connected the wire going to the sender to battery ground through a 3W light and the gauge slowly rose to to the high zone as it should.
I have two sender units. One is OEM, the other is an OE replacement I bought recently. They both have a resistance of about 40 ohms at idle which decreases as the rev's go up. Making me believe they are both O.K.

Finally, I checked the voltage supply to the gauge. It receives 11.9V while the rest of the system is 12.5. It's a bit strange but doesn't explain the gauge reading zero.
All other gauges operate just fine.

I'm just about to give up...
Anyone experienced something similar? Any suggestions or tips will be greatly appreciated.

 

Put a mechanical gauge in and be done all mine have them .

Could be a poor connection where the wire connects to the gauge

Broken wire making intermittent contact allowing the gauge to work

Poor ground where the sending unit screws into the block sealer or teflon tape

Any or all of the above

 

Like wyoming9 said. The temptation is great to put thread sealer or teflon tape on these sending units but that is a big no no. They rely on a proper ground to work and the sealer or teflon tape can interfere with the ground.