Exploding diesel engine

Hi MASH,

Agreed, it's so rare that hardly anyone knows it can occur. In my case having a CO2 extinguisher won't hurt, even if this never happens again. At least I will have replaced/supplemented my old powder one, which can now better be used to mop up oil spills.

Somehow I feel I'm privileged to have been a witness to something so rare and wonderful. Next on the list: Catching falling meteorites in both hands...
 
35mm said:
Using the decompresser, is there is one, would be the first thing to do to stop a runaway!
Click to expand...

Haven't seen any BMC 1.5s with decompressors. And I have seen an exploded run-away. On a trenching digger. The chain drive broke, loose end wacked the fuel pump and off it went. Bit were scattered around for a few yards, with a big hole in the c/case.
 
MASH said:
I hae me doots whether a CO2 extinguisher would last long enough to stop a runaway, physically stifling the airflow is probably the best way, a rag/ dishcloth stuffed over/up the air intake (it'll get partially sucked in which will help)or even a sheet of cardboard or anything else you can hold over the intake until it stops. I also suspect that a powder extinguisher would not work, but it probably would wreck the engine internally.

There are several videos of runaway diesels on youtube and though the noise and smoke looks very alarming I'm not sure its particularly hazardous being close to one. It isn't going to explode after all.

Anyway, it's a very rare occurrence so the chances of it happening to you again is all but zero.
Click to expand...


Very dangerous. SOP is to get the hell away and leave it to its own devices if it gets away.

Glowing pieces of conrod stuck in your head is not conducive to long life.

OP, likely that your motor has picked up on the bore after that shenanigans even if a rod bolt did not let go and ventilate the crankcase. If you are looking to strip the engine you need to have the crank, rods and cam magnafluxed even if they look OK.
Pistons, Tappets and rod studs/ nuts must be replaced as a matter of course. You will need the valves / guides given expert attention too.
 
Last edited:
Lakesailor said:
Toyota self destructs




Insane man hangs on to old thumper





This one has several shots of the crankcase self-ventilating


​
Click to expand...


The last one was a Petrol...:rolleyes:

I had a Citroen ZX once, which was overfilled with oil, and overrevved, even the ignition wouldn't turn it off, so I dumped the clutch in 5th gear. It JUST stopped it!!
 
No Regrets said:
I had a Citroen ZX once, which was overfilled with oil, and overrevved, even the ignition wouldn't turn it off, so I dumped the clutch in 5th gear. It JUST stopped it!!
Click to expand...

When I was about 12 we went on a weekend camping trip for a friend's birthday. In a corner of the field we were camping in (not a campsite, but arranged with the farmer) there was an ancient rusty old tractor. The kind with a solid steel seat on a spring, and no cab; this was in the mid-90s and I'd never seen one like that in active use. Had long grass growing up through it too. We assumed it was a derelict that had been dumped there, and were playing all over it. Then someone must have pushed the wrong switch, and it suddenly started!

Cue a bomb-burst of terrified kids in all directions!

Just as we were realising it wasn't going to immediately explode and an angry farmer wasn't going to suddenly pop out of the hedge, and were coming back to it wondering what to do, my mate's dad fortunately turned up. He climbed up to try to stop it, but like a boat engine it didn't stop on the key, and he couldn't find any other stop control. So like you, he was dumping the clutch into top gear trying to stall it - I swear it looked like the thing was going to jump over the hedge when he did!

In the end he left it in neutral and got off, to look for some vital bit of engine to disrupt, and while he was peering at it it died all on its own - presumably having used up the last bit of fuel.

I don't think anyone ever mentioned anything to the farmer who presumably owned it. No idea whether it really was abandoned or was nominally still in occasional use - but of course the battery had had enough charge to start it!

pete
 
S points to note about a recon engine

ZuidWester said:
Thanks for the info Jcorstophine,

I reckon investing in a completely new power unit makes the most sense in the medium/long term, although £3,500 is a substantial unexpected investment.

The sooner I get working on this the better. All this happened on the last cruise of the year before she gets put in mothballs for the winter. Who'd have thought that would happen. Next year I intend on going on a long cruise with the new engine to make the most of this disaster.
Click to expand...

Just some points to note if you need a new engine (which I am sure you will).

If you decide to go for a rebuilt BMC 1.5 power unit, give serious consideration to shipping your old engine marinising components such as the front engine feet, bellhousing, exhaust manifold, seawater pump, flywheel damper plate and mass weight etc as you would then be guaranteed (I think) that the replacement engine will slot straight in.

If you go for a new gearbox, check what rotation your gearbox is and the reduction ratio so that (perhaps) you can use your existing prop and shaft.

Also check what the drop is on your present gearbox, if it is direct drive then it is usually in line with the centre line of the engine. If the present engine is direct drive and you opt for a new gearbox, then the drop in the output shaft will be in the order of 60 mm so you will need to raise the engine by that amount so that you can line up the prop shaft.

By the way the full engine costs quoted of £2475.00 is for a complete bare engine ready to fit your marinising components from your old engine.

I assume your boat is used on the sea as well as freshwater so you will need and indirect cooled version, the ones listed on the website are for keel cooled which is only suitable so long as you want to fit long lengths of copper pipe to the bottom of your boat.

There is an article in this months Yachting Monthly which give a price of £6400 for a 30HP Beta with another £4000 to complete the installation.

I had this dilemma with my boat when my Ford engine started to smoke and got tricky to start. In my case the cost of a new 30 HP engine would more than my boat was worth. I did a complete rebuild including new head, re-bore new pistons and bearings etc and the cost was about £1600with me doing all the strip down and rebuild plus about £300 for fuel injectors and pump rebuild so the price this guy is quoting is pretty competitive considering he is giving a guarantee.

There may be other companies in the UK which will give you alternative quotes sp worth a trawl on the net.

Had a BMC 1.5 in one of my previous boats and carried out a minor refurb on it with new bearings and rings, reground the valves etc for not a lot of money. Simple engine easy to work on BUT they are of an old design (in fact they were a diesel version of a petrol engine) The new Beta or Nanni will be quieter and may have less vibration.

Any questions, please PM me.
 
Jcorstorphine said:
There is an article in this months Yachting Monthly which give a price of £6400 for a 30HP Beta with another £4000 to complete the installation.
Click to expand...

That was the cost at Recommended Retail Prices. Snooks confirmed on this forum that it all actually cost significantly less than that (boat show discounts, etc), but because he was writing for the magazine he was obliged to quote RRP prices.
 
She's running

I'm onboard now.

Madness maybe, but I got the engine running, having considered I've got nothing to lose by trying. I changed the oil (five litres), manually turned it over slowly and as it turned I could hear the cylinders compressing and then decided to try starting it - I know this was probably not the best move, but hey, I'm on a learning curve.

She started, but only after a lot of "persuasion" using a starter spray as the glow plugs didn't seem to draw any current. As all four cylinders kicked in she sounded just as she always has. I checked the oil pressure and it read 4 bar, dropping to 3.6 bar when idling as it warmed up.
In forward under load it still ran fine, with white smoke from the exhaust clearing quickly as it warmed up. After ten minutes in gear at about 1500 rpm I stopped the engine and checked the oil: Full and clean.

Maybe it's too early to say the engine has survived and the problem has somehow resolved itself, but I'm amazed about this. l briefly entertained the thought that the engine hadn't undergone runway at all, but believe me, it had.

I think I'll work toward replacing the whole power unit anyway and thanks for all the useful information to help me do this. At sea we rely on the engine as the heart of the boat and I don't want this ever happening again, especially not in a storm, at night, on the North Sea.

Fair winds.
 
ZuidWester said:
I'm onboard now.

Madness maybe, but I got the engine running, having considered I've got nothing to lose by trying. I changed the oil (five litres), manually turned it over slowly and as it turned I could hear the cylinders compressing and then decided to try starting it - I know this was probably not the best move, but hey, I'm on a learning curve.

She started, but only after a lot of "persuasion" using a starter spray as the glow plugs didn't seem to draw any current. As all four cylinders kicked in she sounded just as she always has. I checked the oil pressure and it read 4 bar, dropping to 3.6 bar when idling as it warmed up.
In forward under load it still ran fine, with white smoke from the exhaust clearing quickly as it warmed up. After ten minutes in gear at about 1500 rpm I stopped the engine and checked the oil: Full and clean.

Maybe it's too early to say the engine has survived and the problem has somehow resolved itself, but I'm amazed about this. l briefly entertained the thought that the engine hadn't undergone runway at all, but believe me, it had.

I think I'll work toward replacing the whole power unit anyway and thanks for all the useful information to help me do this. At sea we rely on the engine as the heart of the boat and I don't want this ever happening again, especially not in a storm, at night, on the North Sea.

Fair winds.
Click to expand...

Sound like good news,

If as you say the engine has survived, you should check that the fuel lift pump (not the injection pump) is not leaking diesel into the engine. These fuel pumps (AC) have a diaphragm which can leak fuel into the sump and build up a level of fuel. Not a difficult task, usually most of the problems are getting to the unit. It is on the right hand side under the exhaust manifold.

You should get the glow plugs changed as using a starter spray is very very very bad for the engine as it strips the oil of the walls of the cylinder.

With regard to finding a quick way to stop the engine, I would consider removing the usual circular air inlet and get a suitable plug or disc which can be used to block the air inlet. Trying to get a piece of cloth over the suction is fraught with dangers. If you look at the videos, it becomes apparent just how difficult it is to strangle a runaway engine.
 
Don't let it run!

Boat engines can always be put in gear, the prop will provide sufficient load to prevent overrunning. Just put it in gear, do not give it full throttle. Then the engine is not running on its usual fuel and will not develop a lot of power. This should give you the time to think of alternative ways of stopping and prevent damage.
Theo.
 
You must log in or register to reply here.

Share this page

Top