auto engine shutdown for low oil pressure

[gary505]

I was asked if most newer GM cars have an automatic engine shutdown if low or no oil pressure is detected. I know the body control computer is reading oil pressure on most cars but is there software for this safety feature. Owner manuals are no help.

Thanks

 

[Lou Scannon]

I don't know for sure but I expect for liability reason's the OEM would rather replace the odd engine under warranty due to oil system failure than risk getting sued for the consequences of automatically shutting off the engine when the driver, for example, is about to cross a railway track with a train approaching. Worst case scenario, I know, but the deep-pockets are scared sh!tless about liability.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[TheBlacksmith]

There was a low oil pressure shutoff on the Vega. I don't know of anyone stalling on the railroad tracks, but it was fairly common knowledge to many no-starts were traced to a bad oil pressure switch. GM is probably not in a hurry to reuse any technology from the Vega.

 

[LionelHutz]

I don't believe so. The older injected stuff had an oil pressure switch in parallel with the fuel pump relay. Lots of people claim this is a low pressure safety switch. It is not. The switch would allow the engine to start if the relay failed. In other words, crank the engine until it makes oil pressure and the fuel pump turns on allowing it to start. I've ran a few of the fuel injection systems with this "pressure safety switch" missing. It was an odd thing to be installed. Someone at GM likely had concerns about the relay and relay driving circuit reliablily in the earlier injection systems because it was dropped as time went by.

 

[JayMaechtlen]

While figuring out the wiring for my Corvair project, I spent a fair bit of time in the service manual for the donor car- an '87 Olds.
In that car, the signal to energize the fuel pump relay is provided either of two ways.
One path is initiated while cranking, and times out 10-20 sec after releasing the starter switch.
The other is through an oil pressure switch.
While running, if the oil pressure goes away, the fuel pump stops.

- well, now that I think of it, I'm not sure if I ever tested that. Maybe I'll fire the beast up and pull the connector off of the oil sender, just for fun.

cheers
Jay

Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[LionelHutz]

Jay - Try testing it before telling others how it "works".

 

[BigClive]

The Oz Commodore iron-block V6's had a similar arrangement with the oil pressure switch and fuel pump relay. There was always much debate just why things were arranged like this and just what Holden's intention was. I know the fuel pump relay (or fusible link) was inclined to burn out (I had this happen) - so maybe this had something to do with it.

 

[JayMaechtlen]

Lionel-do you trust schematics?


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[mattsooty]

Not familiar with automatic shutdown but I have heard of reduced power & rev limit.

MS

 

[IRstuff]

A typical scenario, much like how the Shuttle launches were configured, is that if the problem is detected prior to launch (engine start), the mission is aborted. However, if the problem is detected during a mission (drive), the problem is noted, but the mission (drive) continues until a hard failure that prevent completion.

Other tactical systems have a failure warning, and the operator decides whether the mission is more critical or preventing damage is more critical, and a "combat override" can be asserted to prevent automatic shutdowns.

TTFN
faq731-376

 

[patprimmer]

I am in favour of strong warnings but NOT automatic shut down. Only the driver can asses the risk of shut down vs continuing at low power or continuing at full power for a short time.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[DanEE]

Surprised that this factor has not been brought up with regard to the use of the oil pressure switch and other means, to kill an electric fuel pump.....

On fuel injected vehicles, the reason for automatic fuel pump shutdown would be the inherent danger in the rupture of a high pressure fuel line in an accident. 50psi is a typical fuel supply requirement on an injected system, and with the use of an electric fuel pump commonly located in the gas tank... the entire line from the tank to the injector rail pressure regulator is at high pressure....

which leads to a severe fuel spill in short order in an accident that ruptures the fuel line any where, not good for possible unconscious passengers in the vehicle.... nor manufacturers..

As already noted above the oil pressure switch is a simple way of killing the pump in an ignition on, after accident scenario, the assumption being the engine will be stopped due to damage in the accident. Of course the "freebie" feature by using the oil pressure switch as mentioned in the original post, is also to kill the engine if no oil pressure for whatever reason..

Toyota ECUs I'm familar with, shut down the fuel pump upon detection of six successive misfires, assumption being there's a big time problem up front or, accident has occurred. Airbags firing on new cars also drop the fuel pump relay.. I would guess some cars use other additional sensors to guarantee the electric fuel pump will be shut off, given vehicle roll over fuel leakage standards and todays liability environment.

Following that same line of thought, the Toyota Prius similarly opens a relay located inside the high voltage battery enclosure for automatic shut off HV power in a major accident, that must be reset through a special procedure.

Uncontrolled release of stored energy is inherently dangerous whether it be gasoline or electricity.

 

[LionelHutz]

Jay - I've retrofitted the GM injection systems that others have sworn up and down started on the relay and then ran on the oil pressure switch. Odd, because I didn't bother installing the oil pressure switch yet they still ran fine.

 

[patprimmer]

Surely there are any number of signals in the ECU that indicate if the engine is running and any one of them could cut off the fuel pump and actually do it quicker as oil pressure would not have to decay to operate the switch and oil surge would not cut the engine

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[LionelHutz]

Pat - Yes, the ECU has no problem knowing if the engine is running or not. And there are much better sensors to use compared to an oil pressure switch when trying to do things like detect an accident or a rollover.