KBlair

Looking at an 83 928S with 120k miles. Owner says that the warning light is flashing because one of the oil pressure sending units is bad, the one that drives the dummy light. He says the oil pressure guage works fine and reads normal oil pressure.

Does this sound right? Supposedly this is the only problem with the car, but how can I be sure if he's telling the truth. He says that he had it checked out by a Porsche specialist and that's what he told him. Also had a compression test done, etc. Said he would provide copies of the inspection at my request, also name of specialist who checked it out.

Are the two oil pressure sending units interchangeable? Can I switch the connections and see if the problem follows?

Also, he sayd that "sometimes" the speedometer will bounce up to 120MPH, then settle back down. Sound like a flaky speed sensor?

TIA

Jay Wellwood

1) There is only one oil pressure sensor. There is an oil level sensor as well - likely that the wiring is shorted/crossed up causing the oil level sensor to cause the blinking !.

2) Speedo sounds like possibly the pickup isn't working properly - or their is an electrical glicth (likely at the connector on the back of the Pod).

3) Go look at the car if you can. If this is the car that you asked if it's a Weissach (sp?) I would look really close. No rear spoiler - doesn'y make sense to me. Be sure to look at the Interior colors as well look for the badge on the dash.

hth-

KBlair

No, this isn't the Weissach. This car is black.

I would go look at it, but it's about 600 miles away.

Thanks for the info, I will grill the owner some more.

WallyP

While there is only one oil pressure sending unit, it does contain two independent indicators. The oil pressure gauge is driven by a variable resistor on the blue/white wire, and the oil pressure warning lamp is driven by a pressure-operated grounding switch on the blue/black wire.

The oil pressure warning on the central warning system is driven by the grounding switch. What he says sounds reasonable.

No, you can't swap the wires or the sensors. You can pull the blue/black wire off and see if the problem is the sending unit or a grounded wire.

The speedometer sending unit is probably OK. It is a pretty simple unit that simply senses the passage of magnets mounted on a ring attached to the differential. The problem is more likely to be a bad connection in the instrument panel.

KBlair

Thanks Wally, I appreciate the info. BTW, I'm just a few miles down the road from you in Dallas, GA. You still in Acworth or in NC now? Suspect I'll be doing some buisiness with you guys soon.

KBlair

Bump, can anyone tell me where the sending unit is located? It's only a $55 part, so I'd like to replace it before the long trip back to Atlanta.

thanks

Kevin in Atlanta

Next to the oil filter. You'll have to pull the filter to get to it.

KBlair

Thanks, maybe I'll just wait till I get back to Atlanta then, it'll be due for an oil change anyway.

Jerry 87 928S4

Be careful disconnecting the tiny nuts that connect the two wires. I broke one stud with very little pressure when I put them back on.

Jim Wilson

Jerry,

I broke one of the studs off myself (see oil pressure sender leak), does this cause an oil leak?
Jim Wilson
'79 Euro 5 I

Jerry 87 928S4

No oil leak because I only broke the stud in th middle. However, the unit may not work correctly unless it makes a good connection.

I played with the stud and nut and got a connection but eventually I got a new sensor - live and learn.

Just glad it wasnt a newer model Shark - you ever price those things! WOW

Jim Wilson

Jerry,

Thanks for the info, looks like that isn't my problem.

Jim Wilson
'79 Euro 5