Dying Diesel

[nevster]

Out in boat at weekend when engine (1.5 BMC Diesel) just died, no coughing/spluttering just one minute running next minute stopped. Have limited knowledge of engines and have assumed that only thing that can stop a diesel like that is a problem with fuel. Have checked fuel seperator ok, have checked and bled system and all seems ok. After about 1 hour and carrying out work engine turned over and fired up as normal. Have I solved problem or do you think there is something else that could have caused engine to stop? Any advice gratefully received.

Mark

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[Rigger]

Any chance you caught something round the prop,which subsequently cleared itself?

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[Guest]

How old is the fuel tank and what material ? If its a lined tank - it is not unknown for the lining to separate and then have a piece literally laying around that can be picked up by the fuel pick-up and the suction can actually cause it to close the line off. Engine stops, flake drops away and engine runs again ....

Only a thought - as I had one that did this many moons ago ..... also knew it happening on a truck a friend of mine had many years ago. Took ages to realiser what it was !!


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[nevster]

I must admit that this had also crossed my mind, prop is turning ok now and being on a drying berth have been able to check as well.

Regards

Mark


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[nevster]

Tank is made of plastic although I'm unsure of age looks ok. Might be some form of gunk in bottom of tank will have to have a closer look.


Regards

Mark


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[Trevor_swfyc]

Agree with nigel sounds like fuel starvation. I would drain down the tank into a container and filter it back into the tank, repeating until the diesel is free of any particulates. Also during drain down check that the flow is uniform if it suddenly slows you know you have a blockage problem.

Have you changed the diesel filters recently or caused air to get into the system?.

Good luck
Trevor

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[boatless]

As Trevor mentions - air - possibly leak in fuel line too?

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[AndrewB]

Not mentioned so far and a bit of a long-shot I admit, but you might have a blockage in your air intake. A quick check of the filter would do no harm. Normally if this happened the engine would have expired rather more slowly with a load of black smoke and unused fuel.

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[bedouin]

I have known these symptoms from an engine that was overheating badly.

Did you try to start / turn over the engine immediately after it stalled - and did it turn over okay

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[sonic]

Hi Had the same problem on a yanmar in my last boat (less than 3 yrs old)it just stopped but would restart almost straight away. changed the filters but still had problem with the engine running ok then slowing down and then picking up revs again.Problem was finally solved when local marine engineer stripped the whole system down and found a large lump of diesel bug in the filter housing intake He had to take the whole filter housing off to get the lump out. I had a plastic fuel tank in that boat and you could see the diffrent colour of the fuel the old stuff was dark red and ended up getting dumped and replaced with fresh clean diesel. I now use fuel additive in boat to keep the bug at bay.

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[muchy_]

Fuel line

I also have a BMC 1.5 and on the easter weekend it did the same as yours. Just stopped. Bled the injectors one at a time and it fired back up. Traced it to a coupling in the fuel line at the tank end. Wiped my fingers under it and there was diesel on them. Dryed the coupling with tissue them tried it again the next day and there was diesel again. No puddles or anything just a slight weep but enough to suck air in and stop the engine.
I was on my way to engineers to have the engine changed. When I got there I told the mechanic and he said that a leak that small would cause the problems that I was having.

Sounds like you could have similar probs.


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[oldharry]

Re: Fuel line

Thats right, Muchy. It takes very little air in the fuel to stop a diesel dead in its tracks. Although the fuel lift pump keeps the fuel under positive pressure in the feed line, each time the hp pump draws on the fuel supply to feed the next injector to fire, the line pressure goes negative - in other words a fairly sharp suction pulse takes place. If any of the joints are at all faulty, a tiny amount of air is drawn in. This may be little more than a few tiny bubbles, but the air accumulates in the pump until there is enough to become compressed in the injector pipe, cushioning the high pressure pulse from the pump and preventing the injector from firing. Result: engine stops dead until the lines are bled.

A very small leak will may allow the engine to just continue to run, but because less fuel is being injected the engine suffers fuel starvation, leading to power loss, usually getting worse till the engine stops altogether, and and often producing increasing amounts of white smoke as less and less of the fuel ignites within the cylinders, or individual cylinders stop firing. This is often the cause of an engine that will only run say 20 minutes at a time - if the tank air vent is not blocked (the most common cause of this symptom!)

Any trace of fuel at the joints in the fuel feeds is suspect, and must be dealt with immediately before it affects the fuel supply to the engine. I always carry a set of copper washers to fit all the fuel pipe unions, in case I have to do running repairs at sea. Only a few pence cost, but could one day make the difference between not getting home!

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[Guest]

Fuel starve or air ....

My truck suffers air leaks and it runs all day and then starts to slow down .... had it sorted 2 times last week ..... luckily I only have it do short trips ..... otherwise its an expensive visit to Merc. Dealer !

Problem is with this sort of fault - it seemingly often cures itself - to re-appear again shortly after ..... Finding the real reason often fails and the action of stripping, reseating the fuel line unions, remiving sediments from tank etc. cures it.

1001 reasons for it and pot-luck which one .....


<hr width=100% size=1>Nigel ... and of course Yahoo groups :
http://groups.yahoo.com/group/gps-navigator/

 

[nevster]

Engine was no hotter than usual. Engine would turn over after stopping but did not fire up until we had bled system (about 1 hr later).

Mark


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[cliff]

I suffered a similar problem with my engine last year. Picture the scene - on wind at all, motoring along quite happily then suddenly engine stops dead. Engine would not restart for love nor money. The problem was not at first obvious but eventually traced to fuel tank and my kids sudden "hard to starboard" maneuver and 360 deg turn to avoid a lobster pot buoy. Remaining fuel in the tank slopped violently to port side of the tank and uncovered the pick up pipe momentarily ~(couple of seconds only) and allowed air into the line. Engine ran fine for a few seconds after the boat had righted herself then died as the bubble hit the injector pump. At least one of the kids had to scrape out their "kaks".

Moral of the story is keep your tanks topped up and don't let two squabbling kids take the helm even if you are bursting for a wee sit down in the head with an old copy of your favourite yachting mag yourself.

Seriously though, sounds like air in the fuel lines perhaps trapped in the prefilter then with the rocking of the boat the bubble could suddenly get into the lift pump and up into the injector pump killing the engine dead in its tracks. Problem is finding the leak.

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[Stemar]

One more thing to check is the vent in the tank. If it's blocked, and especially if the tank is fairly full, the fuel you burn can't be replaced with air, so a vacuum builds up until the engine stops. The seal is never perfect, so a few minutes later, the vacuum fades and you're away.

It's a favourite cause of breakdowns on bikes.

Good luck

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[chas]

I had a very similar problem with a BMC 1.5 a couple of years ago. I tried everything, bleeding, filter changes etc but the engine would still stop suddenly. In the end, I blew down the fuel return pipe (from the FDU back to the tank). It turned out to be blocked. I cleared it and problem solved!

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