What to do with a runaway Diesel engine

[Sorry Pete]

As per title, taken from Wikepedia:

Diesel engine runaway
From Wikipedia, the free encyclopedia

Diesel engine runaway is a common condition affecting diesel engines, where the engine goes out of control, consuming its own lubrication oil and running at higher and higher RPM until it overspeeds to a point where it destroys itself either due to mechanical failure or engine seizure through lack of lubrication. For instance, a 1800 rpm engine can run to 4000 or 5000 rpm or beyond.

Unlike a gasoline engine, which has a butterfly valve controlled by the throttle mechanism to control engine speed, a diesel engine's speed is controlled by varying the supply of fuel.

In many vehicles, a crankcase breather pipe feeds into the air intake to vent the crankcase; on a highly worn engine, gases can blow past the sides of the pistons and into the crankcase, then carry oil mist from the crankcase into the air intake via the breather. A diesel engine will run on this oil mist, since engine oil has the same energy content as diesel fuel, and so the engine revolutions increase as this extra "fuel" is taken in. As a result of increased revolutions, more oil mist is forced out of the crankcase and into the engine, and a vicious cycle is created. The engine reaches a point where it is generating enough oil mist from its own crankcase oil that shutting off the fuel supply will not stop it and it will run faster and faster until it is destroyed.

The unwanted oil can also come from failure of the oil seals in a turbocharged diesel engine, from overfilling the crankcase with oil, or certain other mechanical problems such as a broken internal fuel pipe. In vehicles or installations that use both diesel engines and bottled gas, a gas leak into the engine room could also provide fuel for a runaway, via the engine air intake[2].

The only way to stop a runaway diesel engine is to block off the air intake, either physically using a cover or plug, or alternatively by directing a CO2 fire extinguisher into the air intake to smother the engine.[3] Engines fitted with a decompressor can also be stopped by operating the decompressor, and in a vehicle with a manual transmission it is possible to stop the engine by engaging a high gear (ie 4th, 5th, 6th etc), with foot brake & parking brake fully applied, and letting out the clutch quickly to slow the engine RPM to a stop, without moving the vehicle.


Basically, it's a 'bad thing'. Disregarding wiki's claim that it's a 'common' affliction, it's certainly more common on some models than others. Peugeot 406's iirc were shockingly bad for it. So check your oil levels and those turbo oil seals. This is what it looks like:

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[davidjpowell]

Yikes, Renault 1.9 also had a reputation for doing this when the Turbo let go.

 

[Sorry Pete]

Well, that would tally with the Megane I saw a while back doing this on the hard shoulder...

 

[Norse]

So that is wat it was... My brother once had a VW Golf diesel that would revv up by itself now and then. He had a manual transmission, so didn't have any problems stopping it, but I can see that one can get a little sweat if it should occur in my merc.

 

[moonloops]

Yep a lot of frenchie turbo diesels have this "feature"

 

[BlackC55]

I have had it on an S-class. Scary stuff!!

It made me leg it out the workshop!

 

[Sorry Pete]

Yikes!

Out of interest, was it fubarred? How did you shut it down?

 

[BlackC55]

It shut off after about 40 seconds on its own. It had done 300k too

 

[Mactech]

During the running of the Dieselmax landspeed record car, a runaway engine was a major concern. We were pushing the boundries a bit with over 150bhp per litre form a diesel!
On the check list prior to every run was the operation of the 'strangle' valves.
These were heavily sprung loaded butterflies in the inlet tract, solenoid driven and operated by the drivers right thumb. (Top red button!)
In the event, we never had to use it....but it was there!

 

[G.O'Rilla]

Yikes, Renault 1.9 also had a reputation for doing this when the Turbo let go.

Yes, mine did exactly that when it ate its turbo and putting in 5th, handbrake on - foot firmly on the brake stopped it but I think cooked the clutch. In hindsight I should have let the bl**dy thing destroy itself - I might have got a decent car. Instead, it came back to give me even more unreliable grief.

Not that the Merc has been much better.......

 

[colin_397]

my old series landrover used to do this if you held it at high revs for a long period, ie, motorway. used to smoke its nuts off, so i'd pull on the hard shoulder, stall it and let it cool off for a bit. it was a non turbo so it must have been the rings were seizing.
Funny everyone should say french diesels do it, as my family have had loads of old tired peugeot td's and not one has, yet...

 

[corned]

Saw a Land Rover Discovery in the hard shoulder of the M1 at J29A yesterday afternoon, smoking it's nuts off and the occupants running for cover. You could see the smoke for miles - I thought the whole car had gone up, but as we drove past (I pulled out to give some breathing space) I could see the thick plume of white smoke billowing out of the exhaust.

Scary!

 

[1998K]

this is very intersting and drammatic

What to do with our automatic transmission: is it possible to put in D breaking with both foot operated brake

Car manufacturer should study a proper emergency system i.e. a manual operated lever to close the air manifold, what do you think?

Regards

 

[Colin_b]

Years ago I saw this happen - fitter working on a lorry engine. Over revved, and ran away, huge clouds of smoke, lots of noise and a very loud and expensive bang as the engine self destructed.

It was suspected the driver had 'adjusted' the rev limiter....

Looked rather like this, but noisier and smokier!!!

http://www.youtube.com/watch?v=5zx3qKX_Pno

 

[iscaboy]

During the running of the Dieselmax landspeed record car, a runaway engine was a major concern. We were pushing the boundries a bit with over 150bhp per litre form a diesel!
On the check list prior to every run was the operation of the 'strangle' valves.
These were heavily sprung loaded butterflies in the inlet tract, solenoid driven and operated by the drivers right thumb. (Top red button!)
In the event, we never had to use it....but it was there!

Detroit diesels were known for it, especially the vee engines, the rootes blowers had a similar "panic" flap at the top of the blower (after the turbos on a turbo model) but the only problem was if you used it it sucked the seals off the end of the blower rotors, so you were supposed to change the rotor seals....

So one day I'm working on one, 16v92 (16 cylinders in vee formation, each cylinder 92 cubic inches, about 1,500 cc) with quad turbos, and it starts to run away, sticking governor (injector and pump are integral on a detroit) about to pull the flaps and notice they have clearly been used before, deformed, etc etc, oh ****, this means it will not work... I'm down in an engine room, no way to get far enough away in time.

by the time I grab the fire axe and swing it into the governor oil lines the bitch is doing around 3,500 revs, not a sound you want to hear from a detroit, luckily it worked, because the next option was to dump the fire hose into the intake and hydraulic the engine, destroying it utterly, but safer than a full runaway.

walked off and spent the rest of the day calming the shakes with a drink or beer or ten.

next day autopsy found some numbnuts had swapped around the injector control rods, thus guaranteeing a runaway.

Basically in a normally aspirated engine it is ALWAYS sump dilution (usually leaking lift pump diaphragm) POSSIBLY with a blocked crankcase breather.

With a blown engine it is USUALLY blown turbo seals or blown blower seals, but OFTEN accompanied by sump dilution too.

I have seen an old 5 cylinder AEC half way up a crane run away after some cockney numb nuts overfilled the oil bath air cleaner, it cut the crane in half and the flywheel which weighed all of 500 lbs landed 400 feet away on the other bank of the river.

Despite what wikipedia says, blocking off the air intake will not always work, especially with an old worn engine, they can draw enough air past the rings and past the "blocked" intake to keep going, albeit not actually running away.

Technically speaking a runaway is when the injection pump rack is SHUT, but the engine is running on lube oil, either past the rings, from a blown seal, or due to a leak.

NEVER EVER EVER EVER EVER use any part of your body to block an intake, eg your hand, a runaway is essentially able to pull a hard vacuum, 15 psi, and it will suck the flesh off bones (seen it happen) and carry on going.

Ideally use a block of wood, block, not sheet, something like a piece of 4x2 or 6x4, and have a fall back in case it doesn't work.

CO2 Fire extinguishers are good, IF THEY ARE BIG ENOUGH, if not your best bet is to hydraulic the engine and destroy the piston and / or heads by putting a lot of liquid (NOT OIL) or sand or ball bearings or gravel in the intake.

A small amount of water is worse than nothing, it will make then engine run even faster, forget a hose pipe or water fire extinguisher, you want a fire hose or a bucket of water.

If you get a runaway shut down, DISABLE IT, so that no ******* can start it again, once you've had a runaway that has gone much over redline plus 50% it is a strip and rebuild job.

If it isn't going to shut down, run away, in the direction of the crankshaft axis.

You have between 60 and 120 seconds between it starting to run away of basically exploding. If you don't have it under control in 60 seconds, start running for your life.

Generally speaking, the more heavy duty the diesel, the more danger you and everyone else around you is in, lightweight car diesels are less likely to literally explode, and more likely to throw a rod or a piston.

 

[NormanC]

this is very intersting and drammatic

What to do with our automatic transmission: is it possible to put in D breaking with both foot operated brake

Car manufacturer should study a proper emergency system i.e. a manual operated lever to close the air manifold, what do you think?

Regards

I think that you'd just fry the transmission but you wouldn't stall the engine. So you would end up with an exploded transmission as well as an exploded engine!

 

[1998K]

I think that you'd just fry the transmission but you wouldn't stall the engine. So you would end up with an exploded transmission as well as an exploded engine!

Well understood, thanks!

 

[NormanC]

Car manufacturer should study a proper emergency system i.e. a manual operated lever to close the air manifold, what do you think?

They offer a perfectly sensible device to stop you having a runaway diesel - it's called a petrol engine!!

 

[iscaboy]

If you're going to invoke sense, a diesel can't run away either, it always takes either an idiot to do something stupid, or an idiot to just ignore woeful levels of neglect.

 

[jorjXmckie]

Corned you and I must have been a few cars apart; I saw that too; didn't look pretty, I moved into the outside lane and got out of there pronto!
Was driving back to Worksop from Derby at the time.