Testing an Oil Pressure Gauge Sender

[SonoranSoob]

Hello Sooby World!

I have a 83 Subaru GL, EA-81, with an oil pressure gauge. Since I bought the car, the gauge has sat below 0, moving every once and awhile on start up but immediately coming back to rest at nada. Bought a new oil pressure sender (Not the highest quality one, but new nonetheless), and got it installed but still nothing. When I ground out the wire to the dashboard, the dash gauge rises so I suppose that proves my dash gauge works, but when I ran a fresh temporary wire from sender to the plug that goes into the dash, nothing! I was wondering what a proper test of the actual pressure sender would be. I am pretty sure the sender is a bimetal type, and I've read that cannot be tested with a multimeter. Do I need to buy a certain type of sender to work with my dash gauge?

Very confused, and not much info in my FSM I got off the web. Any help would be much appreciated.

[bushytails]

Gauges that have been shorted to ground get mechanically tweaked to always read negative except at full pressure.  IIRC a 50 ohm resistor to ground should make your gauge read ~75PSI.  Give that a try and see if your gauge is good.  If the gauge only goes up a little with 50 ohms, you can pop the needle off the pin of the gauge and put it back on to show zero instead of negative, and see if that fixes it.

 

[el_freddo]

Other than what bushytails says above, if the sender unit was installed with Teflon tape it might not be getting a good ground through the oil pump and block. 

Make sure all your earthing straps are in good shape too.