When i got my impreza it had a boost and oil pressure gauge fitted. The boost gauge works fine but the oil pressure gauge has got a problem. While engine is off its sits at zero as you would expect, but once the car is running it goes right over to 100 PSI. It doesn't move at all, just sits on max untill the car is shut off. I've had the gauge out and it looks pretty much brand new ( revotec gauge ) and from what i can see all the wires and sender unit look good.
Any thoughts chaps, thanks.

 

seems strange, is the presure sender near the front of the engine bay below the alternator?

 

I'd be suspecting the sender, the wiring, or the gauge.
Firstly, check sender earth with a multimeter.
Can you replace the sender with the OE oil pressure switch and see what the sender does OFF the engine? (You may need to earth it to the engine).

 

the sender is above the alternator,

 

added some pics to help explain.











So basically, the sender unit is connected to the block, the wire from the sender goes to the left hand of the gauge ( if looking at it as in the pic ), a live feed goes to the right hand side of the gauge and an earth goes to the middle of the gauge. There is another wire coming from a tee on the sender which i presume is the original wire for the warning light. On start up the gauge reads 100 psi and stays there all the time, i've tried holding another earth straight onto the sender itself but reading remains the same.
What do we think people,
cheers.

 

any thoughts peeps ???

 

Yeah, do as I asked and refit the standard o/p switch in place of that T-piece, then see what the gauge does with NO pressure on it.

 

The body may need earthing.
Does the dash oil light show red before you start the car?

 

ok, took the sender off the car and tried it, reading was off the scale. Cleaned the tee and the sender and put it all back together. Earthed the sender body, reading was back at 100psi. Pulling my hair out now, thinking i might just buy another gauge and sender. What do you think.

 

Just a thought, what should the pressure be ?? im sure its between 40 and 60 psi. There can't be anyway mine is actually at 100 psi, is there ????

 

??

 

Mine normally reads about 80 psi from cold. Drops to about 45 psi when driving steady, 70 psi on motorway, and 25 psi once warm and idling. Classic MY2000 PPP