Vauxhall Corsa Rev Fault

I have seen this happen with two stroke engines. What is the mileage of the car?

Yes, the engine was running on excess oil.

Diesel doesn't need a spark to run so removing the ignition key made no difference. The oil takes a while to get to the sump so I suspect it was still too full.

I don't know why it reved up to the rev limiter and not further though. You have been lucky that the engine did not go bang. I have seen it happen.

Alan.

Why didn't he put it into gear & with brakes on & stall it?

Diesels will run on & the sulphur smell maybe the cat has destroyed itself with the oil contamination

( snipped-for-privacy@searchlatitude.com) gurgled happily, sounding much like they were saying :

You are VERY VERY VERY VERY VERY VERY VERY VERY

Yes it's running fine now completely as normal.

Not sure why he didn't put it into gear and stall it, panic i guess because we thought it was gona blow up!

it's go> ( snipped-for-privacy@searchlatitude.com) gurgled happily, sounding much like they

The message from "A C" contains these words:

Anyone who will sit and rev a car in neutral "to clear the excess oil" is likely to do all manner of other daft things.

Maybe I didn't explain enough, we were just trying to see if the blue smoke had reduced, which it did. He wasn't revving the engine to excess, nothing like the Revs per minute it shot up to after we had vacated the area when we removed the keys!!

I thought that generally the rev limit of car diesel engines was set just before roughly the point at which it couldn't physically rev itself any higher.

If it was running on its own lubricating oil, by what process or mechanism would it be able to limit what it revved to?

Chris

I'm sure things like valve bounce and an engine's induction/exhaust valve area ultimately have an effect on an engine's maximum revs.

In the OP's case, presumably once the turbo got to the limit of its effective rev range, it would become a partial blockage in the exhaust which would in turn limit the engine's revs.

I guess it would also stop pretty quick if it ran out of oil. (c:

I'm quite prepared to be wrong though.

Yes, of course I understand all of that.

You did say that you thought the rev limit was set slightly lower than the point where it couldn't physically rev any higher. I was trying to point out that when a diesel has gone runaway it doesn't matter what device might be fitted to limit revs because it isn't going to do anything!

One major European manufacturer suggests in their training for service technicians that the safest way to stop a runaway diesel is by throwing water over the engine. The theory is that it will ingest enough to stop it running, but not enough to cause destruction by hydraulicking, before it spreads its innards all over the workshop. Be quite interesting to watch I would think!

Chris

That sounds scary. I'd have thought 5th gear and stall it would be best?

Yes, my point was that if the engine was sooking oil from somewhere, it may have looked like it was revving to the rev limiter (because of the various physical factors affecting how high an engine can rev rather than an ECU or mechanically governed limit) when in fact I thought it entirely possible that it was doing no such thing. I don't think I actually got round to making that point though.

Heh, do they teach duck and cover too? (c:

No, there's no way you would stall a runaway diesel like that! If it was front wheel drive it would just drag the locked rear wheels along; if rear wheel drive it would overcome the handbrake. If you physically prevent it moving either it will spin the wheels or smoke the clutch. Try it if you ever hire a diesel; rev it to the limiter and try to stall it!

Of course, the "throw a bucket of water over it" (!) approach is meant for a workshop situation where any attempt to put a runaway into gear would be pretty risky.

Chris

Well in either case you end up with a lump of scrap. Any amount of water in a diesel will hydaulic it and at that speed easily cause mechanical damage.

The correct way to stop a motor in this case is, if at all possible, is to block the inlet, nothing can run without oxygen. However, I dont think I would like to be that close to a possible grenade at 5000+rpm.

Tim..

That was a foolish thing to do.

Yes. As others have said, the donk started burning the excess oil. Since it isn't using the fuel system, it's not able to be controlled by the normal stuff like the ECU. And diesels running on engine oil exceed the governor... usually bomb too.

Yes, it is... but that limit is caused by the compression of the mixture. When running on engine oil, the limit is different. It's higher. :)

As Chris has said, that doesn't work: it doesn't stall. It either goes bang and the car squirts off, or something else goes bang and the engine keeps on going but you've a broken clutch / transmission / drivetrain component, or if you're really unlucky, there's a bang and a snap, and the front of the car squirts off...

Correct, it's able to burn engine oil much quicker than diesel, so revs higher - reaching silly engine speeds.

Occasionally this happens and bits start breaking off the engine, dangerous if you are in the way.

From a safe distance of course. I've seen what happens to a Clio 1.9 diesel when entering a ford at silly speed. The driver was lucky not to lose a leg.