"Runaway" diesel engines.
Discussion
I thought I would share an interesing piece of info.
When I was at school, I worked summers at a farm. The hillbillies had 2 forklifts, one diesel, one propane. the propane cylinder was very leaky and when the diesel one came in the garage, it ran away completely, it revved its tits off and then exploded.
Since then I am aware that this sort of thing can occur within a diesel engine and is why they have rev limiters.
If you have a diesel engine and you modify the govenor to let it rev more, you are risking a dangerous explosion. The engine runs away and blow by oil causes it to run after the fuel has been switched off. This eventually causes the engine to run dry and whilst at extremely high RPM (unlimited) the whole thing explodes.
Have you guys/birds heard of this and what do you think. Sounds plausible to me.
When I was at school, I worked summers at a farm. The hillbillies had 2 forklifts, one diesel, one propane. the propane cylinder was very leaky and when the diesel one came in the garage, it ran away completely, it revved its tits off and then exploded.
Since then I am aware that this sort of thing can occur within a diesel engine and is why they have rev limiters.
If you have a diesel engine and you modify the govenor to let it rev more, you are risking a dangerous explosion. The engine runs away and blow by oil causes it to run after the fuel has been switched off. This eventually causes the engine to run dry and whilst at extremely high RPM (unlimited) the whole thing explodes.
Have you guys/birds heard of this and what do you think. Sounds plausible to me.
Yeah.....
It actually happened on TV not too long ago on scrapheap challenge when a huge monstrosity based loosely on a tractor with like a 8 litre engine had its guvnor opened by some hill billy dude from wiltshire.... he dropped a bolt. The beast of an engine kicked out a load of smoke and nearly blew good old robert lewellyn to high heaven...... The engine was
ed and had to be replaced...... top tip for life..... never play with diesel engine guvnors, at least dont drop the bolt whilst doing it.
It actually happened on TV not too long ago on scrapheap challenge when a huge monstrosity based loosely on a tractor with like a 8 litre engine had its guvnor opened by some hill billy dude from wiltshire.... he dropped a bolt. The beast of an engine kicked out a load of smoke and nearly blew good old robert lewellyn to high heaven...... The engine was
ed and had to be replaced...... top tip for life..... never play with diesel engine guvnors, at least dont drop the bolt whilst doing it.Yes, I nearly had that happen when an ECU modifier box malfunctioned, however the thing to remember on a modern electronic system is that the ECU needs electicity to function so if you can kill off its supply you can also kill off the injectors which will rescue the situation if things have not gone to far.
Mine happened as I put the car to bed in the garage, had it been at high speed on a motorway where it is difficult to lift the bonnet and dive in things may not have ended so happily.
Mine happened as I put the car to bed in the garage, had it been at high speed on a motorway where it is difficult to lift the bonnet and dive in things may not have ended so happily.
This is a recognised risk on offshore installations - get gas into the diesel intakes and they could overspeed to destruction. Cutting the diesel supply in such circumstances doesn't stop the engine as it's inhaling fuel with the air.
Hence diesels for offshore use are fitted with an overspeed device that slams shut a flap in the air intake if the engine gets out of control.
Hence diesels for offshore use are fitted with an overspeed device that slams shut a flap in the air intake if the engine gets out of control.
This happened on a 306DTurbo I used to drive.
I had been making good progress along a fast A road for about 20 minutes. I approached a roundabout, braked, flicked from 5th to 4th to 3rd and powered on round to 3 o'clock. The engine spluttered slightly before going into free run at maximum revs. I pulled in and turned the ignition off and it continued running flat out for about another 20 seconds. The whole area was thick with oil smoke.
This was a day after a new head had been fitted. Whilst never confirmed by the garage who did the engine work, I'm sure the problem was that oil was being pumped into the rocker cover faster than the oilways could deal with it.
Result: Excess oil plus right hand bend plus turbo pipe at left hand side of engine = VERY SCARY moment.
Fortunately, the 306 had not got to the point where she was sucking up oil from the sump. If this had happened, she would have run at full bore until dry and then seized and there would have been bu99er all I could have done about it.
Happy days
I had been making good progress along a fast A road for about 20 minutes. I approached a roundabout, braked, flicked from 5th to 4th to 3rd and powered on round to 3 o'clock. The engine spluttered slightly before going into free run at maximum revs. I pulled in and turned the ignition off and it continued running flat out for about another 20 seconds. The whole area was thick with oil smoke.
This was a day after a new head had been fitted. Whilst never confirmed by the garage who did the engine work, I'm sure the problem was that oil was being pumped into the rocker cover faster than the oilways could deal with it.
Result: Excess oil plus right hand bend plus turbo pipe at left hand side of engine = VERY SCARY moment.
Fortunately, the 306 had not got to the point where she was sucking up oil from the sump. If this had happened, she would have run at full bore until dry and then seized and there would have been bu99er all I could have done about it.
Happy days
I've had it happen on a Lister-Petter AD1... badly worn bore, started sucking up the sump oil, wouldn't shut off. Fortunately these engines have a decompressor so I was able to stop it with that (bit cruel but needs must).
The scrapheap challenge thing was a bit different... Diesels usually have their maximum fuel stop set at the point beyond which they start belching black smoke due to the difficulty of vaporising and mixing all the fuel with the air in the short time available. At this point they're still not using up anything like all the oxygen in the charge and you can get maybe up to 50% more power by increasing the fuelling, though the combustion efficiency is dire and the black smoke spectacular. They'd probably have got away with it if the guy hadn't unscrewed the stop too far and dropped it, at which point the thing ran away and shagged itself. The odd thing is that there's usually a fuel shut-off lever on the injection pump, which would be right next to the bit he was fiddling with so he could have pulled it instantly and shut the thing down.
The scrapheap challenge thing was a bit different... Diesels usually have their maximum fuel stop set at the point beyond which they start belching black smoke due to the difficulty of vaporising and mixing all the fuel with the air in the short time available. At this point they're still not using up anything like all the oxygen in the charge and you can get maybe up to 50% more power by increasing the fuelling, though the combustion efficiency is dire and the black smoke spectacular. They'd probably have got away with it if the guy hadn't unscrewed the stop too far and dropped it, at which point the thing ran away and shagged itself. The odd thing is that there's usually a fuel shut-off lever on the injection pump, which would be right next to the bit he was fiddling with so he could have pulled it instantly and shut the thing down.
We blew up a rather large bulldozer at agricultural college (moons ago) we'd serviced it & used petrol to clean the air filter - oooops 
Start her up, the thing starts revving it nuts off - holy
it went to about 6k rpm by the sounds of it (normal is about 1500) we literally ran out of the building as this thing went nuts.
Next thing there is an almighty bang & said bulldozers engine is lying all the floor
we got a bit of a bollocking to say the least.
Start her up, the thing starts revving it nuts off - holy
it went to about 6k rpm by the sounds of it (normal is about 1500) we literally ran out of the building as this thing went nuts. Next thing there is an almighty bang & said bulldozers engine is lying all the floor
we got a bit of a bollocking to say the least. A similar thing happened to a freind of mine on the motorway with a Ford P100 turbo diesel pick-up truck. It seems the oil seal failed on the turbo and it started to smoke, so the chap pulls over onto the hard shoulder and shuts the ignition off .... only the engine didnt stop, but continued to rev, belching clouds of oil smoke over the motorway .... and it revved and revved and revved - into orbit, until it had used all the oil in the sump at which point it went 'bang' in spectacular fashion and in the biggest cloud of smoke you have ever seen - took nearly 10 minutes from start to finish!
Of course if he had been thinking clearly, he would have engaged a gear when the engine failed to shut down and then used the vehicle brakes to stall the engine .... cant say i would have wanted to be sat in the thing as it screamed and smoked though.
Of course if he had been thinking clearly, he would have engaged a gear when the engine failed to shut down and then used the vehicle brakes to stall the engine .... cant say i would have wanted to be sat in the thing as it screamed and smoked though.
wedg1e said:
Soton, I wouldn't have fancied putting my hand over the air intake...
Wedg1e, there was so much noise and smoke when it happened, you kinda lose the power of rational thought and it didn't occur to me to try and stall the engine by blocking the intake. Don't know if I would have fancied trying to to stall a diesel running at 5000rpm either. Just as well she stopped herself.
One of the mechanics at the garage who fixed my 306 alleged that exactly the same had happened on a number of Saab diesels which had been run at high speeds for about an hour or so. In the Saab's case, though, the engine did keep on running on engine oil until suffering a spectacular demise
cheesesliceking said:
nobody thought of putting there foot or something they didnt need over the exhaust pipe? stallling the engine?
At 5K revs with more noise and smoke than you ever thought possible. I think most people would just want to get as far away from the blo99y thing as possible
I know i did.
rich_b said:
If you are driving the vehicle when this occurs it is usually possible to stall the engine by using the footbrake in top gear !!!!!
Exactly what i was thinking
OK, You are cruising with the missus on a sunny Sunday afternoon. The world is sweet.
Without ANY warning, the engine just goes feckin' ballistic all the way to the red line. The noise is starting to make your ears bleed. You have just smoked out a significant portion of Dorset blacking out all four lanes in the process. You take the key out of the ignition and it just keeps on going which 'aint exactly what you thought was going to happen.
You seriously think many people would say 'Oh dear oh dear, this is not good. I know, lets select top gear, apply a tad of pressure to the ol' middle pedal and gently stall the old girl' ?
Mine ran for 20-30 seconds and, trust me, rational thinking kinda goes out of the window. Its not to say I might have got my head together after a minute or so but at the time, with the key in your hand and all hell unleashed, it just gets a bit bewildering.
I had my petrol Primula stick on full throttle after it came back from service
Think fast.
Can't turn ignition off, steering lock.
Kick throttle, nope!
Check mats, nope!
Brake, can't drag the engine down!
Ride clutch, nope!
Decision time. Full declutch and risk runaway engine or crash...
Declutch it is then. At this point I realised the value of a rev-limiter as the engine just hit it and cut out and hit it and cut out etc.
Right, need to stop somewhere fast as we are on the way to Cadwell and there's bikes all around. I learned a valuable lesson about servo effect here. With a runaway engine, you have none again.
If you ever get stuck on a full throttle, expect to use both feet on the brake pedal
Turned out they hadn't tightened a clip on the airbox and it vibrated under the throttle quadrant holding it wide open. Two mins to diagnose and fix, much longer "Having a word" with the garage
Think fast.
Can't turn ignition off, steering lock.
Kick throttle, nope!
Check mats, nope!
Brake, can't drag the engine down!
Ride clutch, nope!
Decision time. Full declutch and risk runaway engine or crash...
Declutch it is then. At this point I realised the value of a rev-limiter as the engine just hit it and cut out and hit it and cut out etc. Right, need to stop somewhere fast as we are on the way to Cadwell and there's bikes all around. I learned a valuable lesson about servo effect here. With a runaway engine, you have none
again. If you ever get stuck on a full throttle, expect to use both feet on the brake pedal
Turned out they hadn't tightened a clip on the airbox and it vibrated under the throttle quadrant holding it wide open. Two mins to diagnose and fix, much longer "Having a word" with the garage
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