[McLaren Rulez]

Originally Posted by silversteed

By disengaging the clutch, the engine would not have any load, further increasing the RPM. Remember, higher RPM means more suction and a still further increase in RPM. Beyond a certain point, the mechanicals give way and the engine could disintegrate.

I understand this but a) once runaway has started, the engine is irreparably damaged anyway and more importantly b) the safety of the vehicle occupants and other road users is compromised if the car is in gear and the engine is running away. If it's a damaged engine vs an uncontrollable car at full revs, I'll always take the first option.

Unless there's some other aspect to this, it seems that pressing the clutch is the safe move.

[R2D2]

Originally Posted by Sutripta

I get the feeling that in this case 'car guys' were fooling around with 2strokes!

Actually blokes like me and my friends didn't have the luxury of owning cars as college students in the 1980s.

So our steeds were motorbikes, scooters and even mopeds. All of which were modded to different degrees. Ever seen a Luna moped with an expansion chamber? Yeah! One of my pals had one of those too.

[ringoism]

Originally Posted by SS-Traveller

Used to be not-so-uncommon in the Ambassador 1.5L diesel engines, even without a turbocharger. Related to piston blowby > crankcase vapour recovery circuit, AFAIR. The way to stop it was to yank on the decompression switch and hang on for a minute or two.

The main cause in the case of those old Amby's (and other old-school diesel vehicles like the Trax, etc), was the lack of any solenoid-operated fuel cutoff. The dashboard-mounted plunger used to shut off those engines was not in fact a decompressor, but was linked to the manual fuel-cutoff lever/valve on the injection pump itself. Thus, if such a car - parked on an incline in gear, say - began to roll, the engine turned over and there was nothing preventing normal operation of the mechanically-driven pump/injectors, and once compressing/combusting, indeed the whole car would "run away".

A lot of people in Manali, not having quite got over those old days, still insist that stones must be placed in front of the wheels of parked cars to mitigate this particular risk, even with brand-new electronic-diesel or petrol ones, even when parking with hand-brakes solidly set. Which of course is of little benefit and which makes parking a real pain what with all the stones / bricks laying around. We have been parking the Marshal on a slope daily for seven years now, no brake, just in gear, and never any risk of course; It's old-school enough to lack the turbo, but its solenoid cutting fuel supply WITH THE KEY(!) was something of a technological advance / novelty twenty years ago.


This thing of a bad turbo seal "fueling" the engine had never occurred to me - quite amazing and a bit scary.

Prevention, if not already mentioned, would be to cease driving any turbo vehicle that makes a screeching sound under acceleration - that quite often being caused by the turbine blades contacting its housing, a sure sign that the bearing/shaft is worn enough to be off-center and soon to take the seal out with it.

-Eric

[IndigoXLGrandDi]

I have noticed Oil/Diesel Leakage problem in our Xylo E8 Nov. 2009 which has run around 3,19,940 Kms. I am posting here because I am unclear whether this problem might lead to the Diesel Runaway.

The Engine Oil in this vehicle is replaced every 10000 Kms as against 15000 Kms recommended interval in the Owner's Manual since 1st Oil change at 5000 Kms.

I have used the Engine Oil of minimum CH-4 Grade 15W40 each time.


When I showed this problem to my regular FNG around 5000 Kms and 6 months ago, the owner told me this is due to "Engine hitting Back". This happens due to the Kms racked up by the vehicle.
He told me to use the vehicle as it is as long as possible. Only solution to this is to open the engine/turbo and check what parts have worn out and replace them.

At that time, I thought why to open the engine when there is not drop in pickup and Fuel Efficiency.

But when I went through this thread, I almost got heart attack.


The Photos-
Sorry for the Dirty Engine Bay.



This is the underside of Bonnet-








Please help me trace the cause behind the problem.

Thank you in advance.

[hserus]

Blow by it is called - which can have quite a lot of causes

1. Crankcase breathing getting blocked causing engine pressure

2. Head gasket / turbo blown

3. Brittle / worn seals - your least difficult to fix issue

Take it for a full evaluation at a dealer. You might be looking at a new turbo, or it could be a half / full rebuild

[IndigoXLGrandDi]

Originally Posted by hserus

Blow by it is called - which can have quite a lot of causes

1. Crankcase breathing getting blocked causing engine pressure

2. Head gasket / turbo blown

3. Brittle / worn seals - your least difficult to fix issue

Take it for a full evaluation at a dealer. You might be looking at a new turbo, or it could be a half / full rebuild

I have got the Tappet Cover Packing replaced once in the past. I don't know whether it's culprit again this time.

I think I will have to get the following checked-
1. Worn-out Seals around the Engine,
2. Crankcase ventilation,
3. Head Gasket (I guess the Turbocharger to be ok as it is providing the boost or is it?)

Thank you for advice.

[hserus]

Originally Posted by IndigoXLGrandDi

I have got the Tappet Cover Packing replaced once in the past. I don't know whether it's culprit again this time.

I think I will have to get the following checked-
1. Worn-out Seals around the Engine,
2. Crankcase ventilation,
3. Head Gasket (I guess the Turbocharger to be ok as it is providing the boost or is it?)

Thank you for advice.

Add injectors and EGR to your list.

[Pferdestarke]

Came across this video on YouTube showing a Mahindra Scorpio suffering an engine runaway. Looks like the smoking oil burner has scared the wits out of everyone around!

https://www.youtube.com/watch?v=bB-xGR5vfko

[Rigid Rotor]

Originally Posted by dhanushs

Here's a quick, not very detailed, crude thread on Diesel Engine Runaway - What it is, and how to stop it. Mainly as a precaution thread. ...

Thanks for focusing on this issue, which is not well known!

Besides a leaky oil seal from a worn-out turbo, the other cause also appears to be blow-by gasses from worn piston rings, that is pumped back to the inlet through the crankcase vent line to the intake (in a closed set-up). This was already mentioned by ss-traveller in an earlier post.

The point to note is that in the 'fire triangle' - (Heat-Fuel-Air), the already hot diesel engine now switches over and runs on an alternate fuel - its own engine oil and being a CI engine, revvs to destruct mode despite the diesel fuel supply and electrics being cut off when the key is switched OFF. This is because it has switched to the alternate fuel source that effectively by-passes all sensors, metering and electronics. There are videos of chaps trying to stuff rags into the intake of an old diesel in runaway mode, in an attempt to choke it; only have the rag gobbled up by the engine and it still revving angrily! Its as if the docile Dr Jekyl is suddenly and unexpectedly transformed into the monster Mr Hyde.

I am given to understand that in industrial and marine applications, an emergency air intake cut-off is provided to starve the engine of one component of the fire triangle. Its surprising that such an emergency air intake cut-off has not been mandated by road vehicle regulations.

On that note, there are several You-tube videos of railway diesel-electric locomotives with their diesel engines in runaway mode, smoking and flaming away, apparently out-of control. This includes even current-gen locos with heaps of electronics and safety features - including the new GE Evo series. Again a bit puzzling that emergency air intake cut-off has not been provided - else the crew would not allow the engine to continue in runaway mode.

[ecenandu]

https://www.youtube.com/watch?v=gQLfejnhr54

Looks like a runaway engine.

[Venkatesh.H]

Very informative thread regarding Diesel engine runaway and safety steps to be followed incase of runaway.

Though latest cars are equipped with safety measure to avoid such incidents. Poor maintenance of diesel engines leads to self-sustained combustion / runaway.


Venkatesh.H

[Kosfactor]

Happened to see a old Ford Fiesta in a diesel engine runaway situation - the road was engulfed in smoke and everyone were looking scared as if its going to explode. I could not take a picture of it. This happened near Channagiri - enroute Shimoga.

I think its a good idea to keep a close watch on engine oil level as the vehicle ages.