Ok so I just put in an aftermarket CarQuest Oil sending unit and now my oil pressure is reading the maximum 75 psi ALL THE TIME. Even when Im running at normal temp and the oil is warmed up it still says my press. is at the max. Normally when im in 4th gear and at 2500 rpms the oil press. is about 45ish psi not 75. Anyone know why the sending unit would freak out like this? Is it just a defective unit or is there a certain amount im supposed to tighten the unit? (I tightened it until I couldnt get it any tighter) or somthing like that? Do these things have to be broken in?

if you hold the sender wire from the gauge to earth on the engine block, body or battery - does it also send gauge to maximum ?

 

Or, try disconnecting sender wire from sender unit and see if gauge still maxes out - indicate the wire is earthing somewhere between sender and gauge ? Still got old sender ? How's it behave? I notice some sender units now come with an earth connection as well to ensure good connections so things work properly - no need to make the taper thread so tight it earths throug thread tape if used etc,

if you hold the sender wire from the gauge to earth on the engine block, body or battery - does it also send gauge to maximum ?

 

Or, try disconnecting sender wire from sender unit and see if gauge still maxes out - indicate the wire is earthing somewhere between sender and gauge ? Still got old sender ? How's it behave? I notice some sender units now come with an earth connection as well to ensure good connections so things work properly - no need to make the taper thread so tight it earths throug thread tape if used etc,

I did the first thing you said to do. When the wire is against the block, it gives me no reading (the needle drops below the 0). when away from the block, but not plugged into the sender it gives me a very slight reading (just on the 0). Disconnected from the sender the gauge says the same thing as I said previously (just on the 0). I think im gonna try looseing it a little... see if that helps.

Make sure you have a good connection to the block when you test it. It sounds like you ended up with a idiot sensor, one that turns on a light if the pressure drops below 5 psi or whatever. When you hook these up to a car with an actual pressure gauge, it'll read max pressure when the engine is running, and 0 when it's off.

A 47 ohm resister from sender wire to ground should indicate 45 p pressure

How did you wire it?

I just hooked it up to the old wire that the old sending unit was plugged into. Im starting to think now that it actually may be functional because it will give me lower readings now when Im at idle. Not as low as my old one but better than it was. I thnik it could be that my old one was going out for a long time and was giving me the wrong readings and now this one is showing what my true oil press is. Question: is it possible to have oil pressure that is too high? What is the potential harm to having it high?

The stock oil pressure gauge is unreliable, not accurate nor precise. Basically if the needle moves you have oil pressure, if it drops to zero you don't... That's really about as much information as it gives you. They just plain suck.

If you really want to know your oil pressure get an aftermarket gauge.

 

And yes, you can have high oil pressure. It can be caused by excessive RPM when the engine is cold or something clogging the oil flow, which I don't think I've ever heard of on a subaru.

Dash gage isn't all that acurate either, so it could be reading high.

 

Only way to know for sure is to install a mechanical gage, even if only to test pump pressure.

I have decided to go after my oil pressure sending unit as well. Since replacing the front end seals and belts, the bloody thing has read ZERO.

 

Touching a grounded wire to the sending unit tab momentarily while all is attached gets MAX reading.
Remove the grounded wire, remains at MAX.
Disconnect the lead from the sensor and it will slowly drop to ZERO

This is a SUBARU part...   The sensor is in a different location on the pump body from the previous oil pump. Can't see that mattering (?)

? -- Would an "aftermarket" pressure gauge hook up to the dash display or to a secondary pot gauge nestled into the cluster?

Thank you in advance.

crud, sorry I did a double post

Edited January 22, 201511 yr by Sapper 157

The stock oil pressure gauge is unreliable, not accurate nor precise. Basically if the needle moves you have oil pressure, if it drops to zero you don't... That's really about as much information as it gives you. They just plain suck.

If you really want to know your oil pressure get an aftermarket gauge.

 

And yes, you can have high oil pressure. It can be caused by excessive RPM when the engine is cold or something clogging the oil flow, which I don't think I've ever heard of on a subaru.

ok that puts my mind at ease. thanks!!