polecat702

Is it possible for either the oil pressure sender, or the oil level sender to kill the engine as protection for the engine? In other words would the pressure sender be able to kill the engine if it didn't sense any oil pressure, or could the oil level sensor do the same thing, if the oil pan was empty? I'm just wondering if our cars will do this? I'm getting a bouncing oil pressure gauge reading when the engine is idling and warmed up to operating temp. This is in my 89 S4.

The engines will shut down in my Peterbuilt tractors if ether of these sensors fail, or if in fact there isn't any pressure, or oil in the pan. The ECM, will shut them down as a protection.

worf928

Nope. And Nope. The engine will run without oil. Until it seizes.

The first thing to do on your '89 is to clean the connector to the pressure sender. If your oil pan gasket is leaking - or leaked in the past - the upside down connector likes to accumulate oil. You have to pull it - carefully - and clean out the female pin bodies.

The second - or maybe, really first - thing is to look at the three wires where they tunnel into the rubber connector. It's becoming increasingly common to find that the wire insulation at the connector body has degraded and/or that the copper strands are getting broken. Intermittent open circuit or short between the leads will lead to intermittent bouncing depending upon which way it bounces (e.g. up to pegged or down to zero.)

HTH.

worf928

Also, the circuit for the oil pressure sender and warning go through the jump post multi-pin connector. Bad solder? Corroded pins?

If you do decide to pull the sender connector, I've found that getting it warm (heat gun not a torch) helps a lot.

The senders themselves are robust and don't commonly fail. When the do, they tend to under read steadily rather than bounce.

polecat702

Thanks Dave!!

FredR

I had problems with my 3 pin sender- fitted a new sender, replaced the wiring still no joy. In the end I gave up and fitted a two pin earlier sender- problem solved.

As to whether the sender signal could be used to trip the motor in the event of low oil pressure I would say it is distinctly possible however it would take quite a lot of frigging to make it work and would probably require an additional logic solver and some ind of device to cut off the power supply to the coils. I dare say Ken [Porken] could come up with something in the logic to achieve the same providing he can get the signal into the brains which as I am aware does not happen in the stock configuration.

Koenig-Specials 928

Probably has something like this in the oil circuit and connected to kill the Ignition.

worf928

Quite simple actually: open the trigger circuit of the EZK relay so as to cut power to the EZK. No EZK, no spark and no LH power. No LH, no fuel.

But, IMO, this is a solution in search of a problem. Absent unnoticed 9-12 quart puddles of oil under the car and 'technicians' that forgot to put oil in after a drain, how many 928 engines have seized due to no oil? Not many. If you remove from that set cases of 2/6 bearing starvation, I can, right now, remember exactly none.

For a track car, this might be worthwhile, but you'd want the circuit plumbed into your accusump system so that it only kills the engine if that goes empty.

worf928

Ergo your problem was the front main engine harness.

FredR

I think there was some kind of earthing problem but not in the harness. I had indication issues from day 1 I purchased this 928 but replacing everything in the engine bay did not solve the issue. I think it was Sean who suggested trying the 2 pin sender and as soon as it was fitted my oil pressure indication returned to how it used to be when the motor was fitted in my late 90 S4 before it was wrecked. Just seeing the indication how you think it should be was a big psychological boost even though nothing had changed..

Taguid

I replaced the front engine harness with Sean's harness. He integrated my original 3 pin sender connector with the new harness and I no longer have any bouncing of the oil pressure or the tach which had previously started bouncing about 5k rpm to redline.