cfc928gt

The oil pressure on my '89 GT is pegging all the way to the right side as soon as I turn the key, even without starting, and it stays there even after I turn the engine off until the power goes off to the digital readouts. A new sender is $101 so I'd like to make sure the old sender is truely bad before installing a new one. Is there a way to use a multi-meter on these? If I pull the harness plug off it still does the same thing, i.e. pegged all the way over. There are three terminals on the sender marked G, M and WK. I was kind of surprised when I pulled the plug and started the engine that I didn't get a warning of no oil pressure on the digital dash. Any help would be appreciated.

Robert_H

If I recall correctly, that is exactly the symptom of a faulty sending unit. Mine is the exact same way.

G Man

$100.00 for an oil pressure sender? WOW. Time for someone to find a cheaper alternative. Kind of like the motor mount situation.

cfc928gt

Yeah, the '89 and up use a different sender. Earlier ones are still pretty inexpensive.

928Modeler, thanks for your reply. I wait and see if I get anymore input before I bite the bullet.

borland

You'll need to buy a 1-1/16" combination wrench that you can modify by beveling the inside edges of the open end. You'll need it to counter hold the threaded plug (oil thermostat housing) while you remove the sender with a, I think 7/8" opened end wrench. If you don't counter hold the plug, it has a tendency to unscrew with the sender.

You need to bevel the inside edges so both wrenches fit in a limited space and match the beveled edge of the threaded plug.

borland
90' S4

SharkSkin

Which harness plug are you referring to? If you're saying that when you disconnect the wires at the sender the gauge still pegs with the key on, it sounds like the problem is in your wiring, short to gorund somewhere.

tw1963

Mine just corrected itself after I had the instruments apart to do the odometer gear replacement.

I had the same symptom and tried a different sender with no change. The gauge is now working perfectly since the instrument panel R&R and clean-up.

YMMV of course.

Cheers,

Terry

'85 Euro

David Green

Did you resolve this problem - I have exactly the same problem with my 89 S4 with digital dash ?

Bill Ball

Almost always a bad sender.

IcemanG17

It does sound like a classic bad sender......pegged at 5 bar all the time...bummer its so steep....

http://www.mailordercentral.com/928i...606%20203%2003

$108 for the 89+ and $95 for the older....

David Green

What I don't understand with this problem is that with the harness plug in the engine bay disconnected i.e. the oil pressure sensor is not connected - it still shows +5 bar.

Chuck Schreiber

Can also be that the leads are switched. When I put the new one in the 79 it did the same thing, always pegged on 5 plus bar. When I switched them (the leads), the gauge worked properly.

Bill Ball

The sensor circuit provides a resistance value to the gauge. The resistance is HIGHER at HIGHER pressure. So, if the sensor goes open circuit (infinite resistance), it reads the maximum pressure all the time.

David Green

So if I were to ground out the wire with the power feed (blue and white I think) effectively bypassing the sensor it should in that case mean the gauge will read zero - is that correct ?

cfc928gt

Just saw this thread and yes, it was a bad oil pressure sender. You also need to replace the oil thermostat if that hasn't ever been done. That gave me 0 pressure readings on hot startups and it increased my coolant temps since it wasn't sending hot oil to the cooler.