JPTL

Getting ready to do an SCCA PDX (like a DE) at Summit Point this weekend.
We're running fresh 20w - 50 with a new filter in the '88 S4.
The car has been running beautifully, but I can't help but notice that the factory pressure gauge stays pegged just above the 5 bar, whether at 4k or at idle as in the pic below.
Since the gauge stays pretty much pegged, I don't see much fluctuation in rpm's.
After the engine shuts down, it smoothly settles to 0.

Is this a normal reading in a healthy S4 w/fresh 20w-50 at operating temps?
I've read this thread from the archives, and started to think about a stuck relief valve, until Jim B's comment that the relief pops at 9 bar. I'm not seeing/smelling any oil seepage...
Any ideas? Should I be concerned?

Mike Frye

Hey JP!
I'm thinking it's electrical.

Should be lower once the car is warmed up and at idle (middle of the gauge or so) going up to right at the top line but not over it at higher RPMs.

How about with the key on and engine not running? Does it move at all?

SeanR

If it doesn't drop, after the oil comes to temp, at idle then you have a sender/wiring issue.

JPTL

Hey Mike/Sean,
Mike - key on to ACC, it pegs to 5. Start it up, it flickers for a split second, then pegs to the top of the gauge.

I'm thinking troubleshooting the oem gauge and wiring might take more time than installing an aftermarket gauge (and I suppose sender).
If that's the case, what would be the cheapest and quickest way to get set up with a dash mounted aftermarket gauge? No time to wait for shipping
..or, is there a quick test/easy access that might reveal shorted wiring or a bad sender?

worf928

Connections to oil sender are reversed. Or, at least, reversing connections with good wiring and good sender will cause described behavior. Could also be smooshed harness.

JPTL

I was allowing the "Search" button to be my friend, and reading this thread when your post came in, Dave.
Thanks for chiming in.
I'll try the wire swap and see where it gets me....

Alan

It certainly isn't 5 bar at hot idle - whatever oil you are using - so its lying to you one way or another

Alan

Bilal928S4

Could it be a cooked sender?

JPTL

Just got out from under the car.
Connectors: one's a spade terminal - one's a ring, so getting them swapped wouldn't be as easy as I thought....
Instead of swapping them, I pulled the spade and checked key on, engine off. Still pegged above 5. Started the car and it behaves as before. Pegs at 5.
Shut off engine, turned off ignition and checked the continuity at the sender between terminals:
no continuity
Checked the continuity between the pulled spade and the still-connected ring:
no direct short
Checked the resistance between the pulled spade and the still-connected ring (key off):
1.1 kΩ
Would this tell me anything?

depami

High ohms = High pressure.

Low ohms = Low pressure.

One wire is for gauge and one is for light. Ground is through sender body.

Gauge ohms are variable and linear, light signal is open or closed.

With wires unhooked, gauge will be pegged at max and light will be off.

With wires grounded, gauge will be zero and light will be on.

Manipulate wires and check for above indications.

If above proves true, wiring is good. If not, wiring is bad.

Mrmerlin

^^^^ Denny thanks for the simple but succinct testing description.

JPTL

Now the proverbial wrench got thrown into the mix:
While gently tightening the little nuts on the sender studs, one stud f*ing broke off along with a little wire probe that obviously goes up into the sender to make a connection.



I assume the oil needs to be drained before replacing a sender - assuming I can find one tomorrow....
VDO?
FAE?

JET951

Porsche / VDO only . nothing else will work as well / reliable , this is one part in which you get for what you pay for

depami

I cheaped out and bought a FAE. It is junk. Not sure if they all are or if I just got a bad one. The light contacts are not consistent. The gauge appears correct. I unhooked the light wire to not be bothered by it. It will be replaced but not with another FAE.

JPTL

Thanks for the advice. I'll try to source a used oem. Probably better than anything new in the aftermarket department...

I'm waiting for someone to tell me that I won't need to drain the oil

That boat still hasn't sunk, Denny?