cwiert

I hope I can explain this clearly...

On my '88 S4, the oil press gauge remains pinned at 5+ all the time...even with the engine off and key removed. If I then adjust my instrument pod up and down a few times I can jostle it loose and get it to fall back down to 0. But as soon as I turn the key to the #2 position (where all the instrument warning lights go on) it will pin itself back to 5+ again... and I never even started the car. The only way to get it to go back down again is to adjust the pod with some force again. I don't even know where to begin with troubleshooting this problem. Any ideas???
Thanks,
John
ps - I guess my first question is this... When you turn the key to the #2 position (before starting the car) where the warning lights go on, is the oil press gauge supposed to go up to the 5 position as sort of a test, or is it supposed to remain at 0???

Leon Speed

Supposed to stay at 0, until the engine runs (cold: 5 bar, hot: anywhere between 1 and 3 bar). So when you adjusted the pod down, and the gauge is at 0, when you start and run the car, does it go to 5 bar and then to 1-3 bar (at idle)?


There are a few items you can check. As you say when you move the pod, the gauge will change. So start by cleaning the connectors to the pod - there are 4; you will need to remove/loosen the pod to do so. Second, clean the ground behind the dash under the pod. Third, the oil pressure sender could be bad, but it doesn't sound so from your problem description.

cwiert

No. As soon as I turn the key 2 clicks the gauge pins itself past #5. After I start the car and let it warm up and idle, it still remain pinned at the same spot. It won't budge again until after I shut off the car AND violently move the pod up to jostle it loose and it will then fall back to 0. I tried jostling it while the car was running, but it wouldn't budge. Very odd indeed.
I'll clean those connectors as you mentioned along with that ground point. Hopefully that will help.

Landseer

Do you have a copy of the wiring diagrams? They are pretty much indispensible for shark owners doing the work themselves. Sometimes the OP reading is compromised at the gauge, sometimes at the CE, or the 14 pin connector or the gauge itself. The diagrams help you trace the different portions of the circuit on this and the other areas that you are sorting.

Nice blue shark, BTW.

Stromius

Here's results from a search (https://rennlist.com/forums/3011651-post3.html). Is it possible you or the PO reversed the oil pressure sender wires? Otherwise the sender may need to be replaced.

cwiert

Thanks for that link. I've read a bunch of threads on this issue and it looks like, most commonly, this is a typical scenario when the wires are reversed on the OP sender. That will be the first thing I check.
I see it written in other threads that the OP sender is near the oil filter, towards the front of the car. I'm still learning this car (only 3 weeks old)... I assume the only way to get to it is by lifting it up and getting to it from underneath?

928 at last

Only access is from below.
And,
Common failure point is the wires into the plug which fits to the sender itself. You may want to check these first.
If all is well, the sender itself is likely the problem.
In this case, best to deal with it while you're doing an oil and filter change.
The sender is a PITA with the oil filter off. On I wouldn't even try.
You will need a short (Preferably thin) 24mm (I think that's the size....others please feel free to correct me here) wrench to get the sender out.
I got caught short last weekend, (pardon the pun and other potential references) and actually got lucky with a short adjustable wrench. Not the recommended approach by far, but worked for me.
After re&re. It was ultimately the wires that were the problem.
Oh Well...It's all new now.

Maleficio

Yep, you gotta jack it up. Two terminals on the sender with rubber boots.

cwiert

just to follow up with this... it was the oil pressure sender. I replaced it and everything works fine now. and it wasn't even that bad getting the sender out. Once i took the oil filter off, I was able to fit a small adjustable wrench in there to get it off. thanks for all the help.

SQLGuy

When I got my car it was doing similar things. Turn on the key, engine not running, it would show 2 bar. Running, it would always show 5 bar. Replaced the sender with one from 928sRus, and it's good.

tveltman

I had the same problem. I tried swapping the wires to no effect. I swapped out the sender and the problem went away. Gauge worked perfectly. I would guess that you could put a voltage on the wires that come off of the sender and see if you can make the needle move. (or maybe current or something, I'm not sure what signal the sender actually sends, but that would be the easiest way to isolate a dead sender). I'll see if I can find something about the output signal.

Andy Kay

I had the same problem on my 911 SC last month. It was the oil pressure sender.

Hey, why do they call the 928 guys "sharks"?

tveltman

All lawyers and politicians?

haha no it's the term of endearment we give to the 928.