fortysixandtwo

It could be any of those (filter is doubtful), or a: cracked pick up tube, loose crank bolt, damaged oil pump, separated case sealer at pump or lower block joints, pickup tube seal, worn bearings.

For your wallet's sake, I hope its just a failed sending unit.

Dal Heger

What year is your 951?

If its an 86, then it has the old style oil pressure relief valve that's prone to sticking open. Could be that it got something stuck in the ball seat, or if it's a 87+ gunk in the piston of the new style oil pressure relief valves, and it's sticking. Been there, done that, remove and clean the oil pressure relief valve (yes, you can take apart and clean the new style valves, check to make sure it's not scored inside).

Good luck.

kmm944

Thanks, I apreciated, by the way it is 1986 951, lightly moded, engine resealed and new belts few hundred miles ago. Like I said I am still to check the cranck bolt but very confident with the correctness of that, I am onto the feeling of OPRV or bad sender switch since it does flicker at very light taps of the accelerator, and the " ! " and low oil lights will disappear for like a couple of seconds!

kmm944

I'll be checking pressure sender with DVOM since its the simplest thing to do. I still did not find a mechanical pressure gauge, but that will be next, then I'll check OPRV... Keeping the hope for a faulty sender folowed by the OPRV and truely hoping it ends there!!!

BigMikeATL

I had the same thing happen to my 85.5. I wouldn't start the engine again until I checked the oil pressure relief valve in the oil cooler. The one in my 944 broke. I R&R'd the oil cooler seals and relief valve and it was good to go.

kmm944

Was your engine sounding unhealthy when it happened and if it did what was it like?

zerMATT951

You could short the contacts and see if the meter pegs...

BigMikeATL

Not at all, it was extremely tight. Even when I sold it at 140k miles, it only used about 1/4 quart of oil every 4k miles.

The good part about it was that I was going to do the oil cooler seals as preventative maintenance anyway and had the parts. Only needed to get the relief valve. The job is a total PITA, but doable without a lift. But a lift sure would have been nice!

kmm944

I R&R the OPRV, it is the old type but in very good condition with a strong spring and it was free sliding without any binding! I will save the money for now. I am wondering if I should just get the oil filter relocation kit with additional ports and simply hook mechanical pressure gauge!?! It's less than a hundred bucks and it's very convenient for ease of access! Also it's cheaper than a oil pressure tool which is about $200.

kmm944

I thought one lead was pressure signal and the other is the low oil light???

fortysixandtwo

Your understanding is correct. One lead drives the sensor, and the other activates the warning light. Technically there is a third lead, which would be the sending units body (grounded to block by the threads)

Shorting the warning light lead to ground (touching it to the block) should cause the low oil pressure light to come on. I haven't tried this, but it makes sense.
Shorting the gauge lead to ground should drive the gauge to read zero oil pressure.

We already know the warning light works, so that part of the harness is not in question. The pressure part of the harness is probably okay as well, because if there were an intermittent break, it would peg the gauge at 5+ bar then come down to actual reading levels when the signal is regained. I suppose there could be corrosion build up, in the circuit, causing a false reading, but the likelihood of the warning light malfunctioning at the same time, is very unlikely.

The only way to test the sending unit is to either remove it, apply a know reference pressure and see if the resistance is correct for that pressure, or install a separate oil pressure monitoring device (mechanical gauge or separate sending unit & electronic gauge) to the car and compare the readings.

You can pick one of these up for installing a mechanical guage
http://prosportgauges.com/oil-filter-adaptor-plate.aspx

I think you will have to use a metric to standard adapter to install a typical mechanical gauge, some gauges may come with such an adapter. Or you can drill and tap one of the ports out to fit the standard pipe thread.

You can also throw some money at it and buy a new pressure sensor in the hopes that its the problem.

kmm944

I was actually going to do that, remove the sender and while still attached to the instrument cluster, I was going to pressurize it with a manual hydrolic cylinder pump that I got liying around. The pump has a built in gauge in psi. Even if it's not completely accurate, it will still show me if the sender is ok!

kmm944

I apologize for my ignorance.., testing the oil sender is descriptively guided thru "Clarks-Garage"...

F18Rep

You need to shop around. $45 and thats with the adapter...;] Bruce

kmm944

This is not a bad price but I already purchased the oil filter sandwich adapter plus I have couple of brand new oil pressure gauges that I will be hooking up to (one of them), to the port of the adapter! I will leave the set up in the engine bay, just so i can have a reference point!