Maybe a silly Q but - how does one stop a Diesel Engine running ?

guernseyman said:
The stop solenoid on my engine is actually a run solenoid - activated to allow fuel to flow. When the key is turned to off, power is removed and a spring operates to cut off the fuel.
A few years ago the solenoid burned out and the engine stopped soon after leaving the marina.
Discussions over a long period led to a modified solenoid being fitted in which the spring allows fuel to flow and a push button operates the solenoid to stop the engine.
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This is how the vast majority of boat engines with electric stops work. What engine was this on ?
 
PaulRainbow said:
This is how the vast majority of boat engines with electric stops work. What engine was this on ?
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Having a solenoid always enginised while the engine running will require a continuous rated solenoid where as if you have a solenoid used to stop the engine the current only needs to enginised until the engine stopped running then once stopped the solenoid can be deenginised. This means an intermittent rated solenoid which will be cheaper to make.
 
Many years ago my old air cooled VW bus was in need of a decoke and would carry on running for about 30s after turning off the ignition. I assume the red hot carbon and the fuel in the float chamber kept it ticking over while I locked up and walked away. I expect most cars now have an electric fuel shut off to prevent this happening.
 
Rogershaw said:
Having a solenoid always enginised while the engine running will require a continuous rated solenoid where as if you have a solenoid used to stop the engine the current only needs to enginised until the engine stopped running then once stopped the solenoid can be deenginised. This means an intermittent rated solenoid which will be cheaper to make.
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Pre common rail cars had solenoids that energised when the "ignition" was turned on and de-energised when it turned off. Commonly just a plunger with a seal o the end that closed the flow of fuel. As an emergency "get you home" if the solenoid failed you could remove the seal and the engine would keep running. You'd have to stall it when you got home.

Almost all marine engines work in the reverse, the solenoid normally allows the engine to run and requires energising to stop the engine, either with a stop button or a stop position on the key switch. These are, as you rightly say, intermittently rated. You might want to tell Volvo they are cheaper to make, they charge an outrageous £400 for the solenoids on the 6 cylinder engines. If the Volvo solenoid is left energised for a while it gets extremely hot and can melt internally, potentially causing a fire.
 
Resolution said:
Not a silly question at all Popeye. I know from first hand experience how embarrassing it is when you cannot stop your engine. A couple of years ago, prior to the first outing of the year I fired up my Yanmar to check all was well. Battery fine, started immediately. Ran it for 15 minutes to warm everything , then went to the cockpit and pressed the red KILL button as usual. No change, ending running smoothly as ever. Assuming the contacts in the red button were corroded I shorted out the two wires to the button; no change. Slightly worried, I rummaged down below and turned the fuel supply lever to OFF; still no change. Dragged out the Yanmar manual, expecting to find some lever down by the injectors that would cut the fuel; pathetic manual with diagrams drawn by a spastic, no mention of a KILL lever. Went on YouTube for help. Read and half understood that the fuel supply lever was probably thwarted by the return fuel system. One suggestion was to cut the air supply instead, so I found a suitable size wooden plug and rammed it up the air filter intake; engine half throttled, but manfully refused to die completely. Removed the bung. By now it was Saturday evening, no engineers within call out range, so we sat down to supper with the engine burbling away happily. Fuel tank was full, so at least no danger of clogging the injectors with whatever gunk lies at the bottom of the tank. Went around all the other boats in the marina to see if anyone had any new ideas. Lots of helpful (!) comments. Went to bed. About tennish next morning (Sunday) a very nice pal turned up with his Sunday lunch guest, who he said was an engineer on a cruise liner. This poor fellow was all in his posh weekend clothes, but he stripped off and set to to examine the engine. Of course he quickly identified that we have a fuel cut off operated by a solenoid (not marked in the Yanmar manual....) but that my solenoid was well and truly rusted solid. To his enormous credit, he set too with a spanner or two, working over the top of a very warm engine, and managed to cut off the fuel supply. My hero!!
When the Yanmar engineer arrived to replace the solenoid, we took great care to identify exactly how to get a long rod in behind the solenoid to operate the little lever that does indeed cut off the fuel to the injectors. End of a very bad start to the holiday.
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Unless your fuel tank drawoff is at the bottom, letting the fuel level get low won't draw up crud from the bottom of the tank.
 
my old engine is a 1.5 litre 4 cylinder.. Rotary injector pump.. the pull stop cable worked less and less and if pulled now it speeds the tickover up..
I place my palm over the air intake and it stops instanly. It doesnt suck a lot more than what pressure your mouth can crate on your own finger..
its easy access so easy to do for me, but still a pain .
Its the ball ache of having to take the pump off and send it away to fix it that has made me live with it for the past 3 years.
would never dream of using my hand on anything other than tickover.
 
It's absurd to claim that the vacuum is so strong that the oil (incompressible fluid) is just sucked out somehow so the air cut off valve doesn't work. A vacuum is at most 15psi, and air cut off valves are absolutely a normal thing, 5 seconds of googling will turn up hundreds off examples: here's the first I came across.
 
PaulRainbow said:
Pre common rail cars had solenoids that energised when the "ignition" was turned on and de-energised when it turned off. Commonly just a plunger with a seal o the end that closed the flow of fuel. As an emergency "get you home" if the solenoid failed you could remove the seal and the engine would keep running. You'd have to stall it when you got home....
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ISTR Cummins had a knurled screw on the solenoid to open the valve if there was no electrics. To unscrew for shut down meant putting your hand between the pump and the hot engine block - not nice!
 
Rogershaw said:
Well as an Professional Engineer I tend to look for proof and anm not into blind faith.

There has been sever posts where blocking the air inlet is a safety requirement and in some cases a legal requirement

So forgive me if I find it difficult to understand and believe you as its been considered an acceptable way of stopping a runaway diesel.

If you have a video of this happening I am willing to review and get comments from the wealth of knowledge on the forum
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I have seen almighty messes being caused by partially blocked air cleaners and oil being sucked into the intake via the ccv on both Cummins and cats and mtu with the Racor type ccv and mtu have a similar system. (Engines didn’t run away though)

not seen it on a Volvo, they don’t have such a direct link in either the d series or older ones I guess. Not to say it hasn’t happened

I’m going to take a punt and say until fairly recently the machinery on the rigs just didn’t have ccv’ or if they did there’s a valve to shut that off as well as the intake.

the old pac 22 ribs for the navy had a flap actuated by a solinoid the went over the intake on the mermaid diesels in case they ran away. Latterly a few used them for a kill cord arrangement. (they had no air cleaner though)

of course if it’s running correctly neither operating the decompression leavers (results in the mechanism getting smashed up if your unlucky) or covering the intake is very advisable!
 
Boater Sam said:
Which engine do you have Popeye? There are several very different ways that the engine normally stops.

In emergency loosening the pipes to the injectors will stop any diesel, mess but fool proof.
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Easier just to block the air intake. The oilfield engines I used to work on were actually fitted with an emergency flap in case gas got loose, diesel engines will run on gas being sucked in to the intake. On Detroit diesels they fit flaps as std, they will run on their own lube oil if the supercharger oil seals start to leak, which they could and did do!
 
I had an old Yanmar YSB8 on my last sailing boat, a Van De Stadt 26' fin keel, that went into self ignition mode of its own oil when on the sea trial with the would be buyer, and that briefly propelled that old sailing boat to ~8 knots, the smoke and nooise coming from the cabin was unbelievable, and it only stopped when the head gasket blew. I did think about obstructing the air inlet but decided it was safer to keep steering and not go below in case it exploded.

Amazingly the buyer was not put off although I did fix it plus I then included the 8HP longshaft Yamaha that until that point was not included in the deal. The broker was also astounded, as well as slightly shocked.


The Cummins 6BT range are energise to run - and the solenoids can be troublesome if not assembled properly by the pump repair shop !
 
Remove air , compression or fuel a diesel it will stop.
I don’t know enough To argue about shutting of the air. Theoretically it will work, I accept you have to be able to shut off all the air or it will draw from somewhere else.
so might not be the best method.
De compression, open the leavers, I’ve seen it done. Not a good idea. Likely to cause damage, it does work. On a small engine.
On a big engine flames just shoot out the cocks.

Shut of the fuel strikes me as the best bet. My engine shuts down by activating a pull lever to shut of fuel supply.
fitting an additional valve a the fuel tank has always seemed like a good idea.
Particularly if it could be done remotely.
normally a requirement on commercial vessel.

Im pretty sure my engine would stop if I opened the fuel filter and let air into the system. I would have to bleed it to get it running again. Never tried it, could get it to start start after I opened it to clean. Had to bleed it.

loosening fuel line at injectors ect would work but extremely difficult to get at on my engine. So not a good plan.
 
Uricanejack said:
Shut of the fuel strikes me as the best bet. My engine shuts down by activating a pull lever to shut of fuel supply.
fitting an additional valve a the fuel tank has always seemed like a good idea.
Particularly if it could be done remotely.
normally a requirement on commercial vessel.

Im pretty sure my engine would stop if I opened the fuel filter and let air into the system. I would have to bleed it to get it running again. Never tried it, could get it to start start after I opened it to clean. Had to bleed it.

loosening fuel line at injectors ect would work but extremely difficult to get at on my engine. So not a good plan.
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That is all good .... although the discussion has moved on somewhat from how to shut down the engine under normal circumstances, when shutting off the fuel is not contested, to shutting down the engine in a runaway situation. In the latter case the fuel cannot be shut off.

Richard
 
Uricanejack said:
... I don’t know enough To argue about shutting of the air. Theoretically it will work, I accept you have to be able to shut off all the air or it will draw from somewhere else. ...
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It is not a theory, it is a practical fact and devices are fitted into some air intakes of diesel engines to shut off air in an emergency shut down event. See my earlier post for examples of the devices.

On a boat, many small engine air intakes are baffle types at the inlet and would be difficult to seal e.g. my Perkins 4236 has a mushroom air inlet filled with a filter material, so shoving a rag over it would not be effective nor could it have a bung inserted without removal of the filter element from the manifold. As the only external large gas volume leaks is post Curry nights, I think the risk of runaway is low.
 
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