Help! Engine mystery, potentially dangerous

Going back to the original problem, if it didn't exist in the past, you must consider what has changed or what has been done to cause it. For example, have the filters been changed? If so, and air leak could have been caused by this. (I keep banging on about air leaks from filters because your symptoms are exactly what we experienced). If you have dismantled some of the fuel lines, the problem could be with a joint misaligned or slightly loose. I think the comment about proper fuel clips being used instead of jubilee clips is unlikely to be the cause of the current problem as presumably the fuel system has been working satisfactorily for the past 15 years.
 
It could be an air leak, put talcum powder over every joint and the bleed screw. When air is sucked in diesel leaks out so run the engine and slow it down until stops then wait ten minutes and check for diesel.
 
ghostlymoron said:
I think the comment about proper fuel clips being used instead of jubilee clips is unlikely to be the cause of the current problem as presumably the fuel system has been working satisfactorily for the past 15 years.
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15 years old flexible fuel pipe is not as flexible as new stuff. Poorly fitting clips won't help.
 
ghostlymoron said:
Fascadale, don't keep us in suspense, have you cracked it? And if so what was the solution. I hate unsolved mysteries.
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Thanks for your ongoing interest

The story so far...............................

We took the advice of the excellent John from Beta and put in a "Pigs Tail" as well as sorting the other joins on the return system. (Using top of the range clips) That was in Camaret. The passage to Guernsey was excellent, the engine only ran for about 12 hours before our arrival and it performed perfectly. I was so pleased I tried to post some photos but was unable to get them from my phone to Photobucket.

The passage from Guensey to Lowestoft also went well but we ran out of wind once we had crossed the channel. The engine ran perfectly for over 24 hours but unfortunately cut out on a trail "slow down 5 miles short of our destination. I left it to cool and then it was fine on the way in. Puzzling or what.

I'm tempted to do Lowestoft to home ( Edinburgh) in a oner, the passages are fine, its the arriving that's difficult

Thanks to all who have been so generous with their advice: there will be an update with photos when we get home.
 
Even more baffling. It doesn't now sound like air leaking in as it starts again after cooling down. If air was getting in, you'd probably have to bleed it to get it started again.
When did the symptoms first appear? It must be something that changed or deteriorated.
 
have you checked the throttle cut off valve isn't to close to the limit re adjustment and once heated up turns it off
 
savageseadog said:
It's loose debris in the tank or somewhere in the pipework.
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Years ago we had this problem, caused by rust flakes in the fuel tank. I assume the outlet from the tank would become blocked by a larger one. Symptoms were not exactly the same as the OP's but similar. Before changing the tank i became quite adept at disconnecting the fuel supply from the lift pump, attaching a short length of plastic hose and blowing the fuel and debris back into the tank. This always fixed it but was less than convenient. I remember doing it between the point and the isolated danger mark at Porth Dinllaen, a gap of less than 100 metres. Don't panic!
 
+1 for vyv-cox rust flakes.

Another suggestion. I looked at a compressor which did much the same...started cold most times, ran well under load, but cut out on idle and wouldn't restart. A new injection pump had been recommended. After some head scratching, I removed and inspected closely the suction lines, and replaced them. It turned out that minor stress marks under the clips were allowing enough air in to upset the pump at low speed, i.e.low suction, when warm. At high load, the suction was higher and I think must have sucked the hose on just enough to maintain flow. As for starting from cold most times, I can only think that there was sufficient fuel in the pump, and with the automatic full governor setting, it kicked off.
There was actually no visible diesel leak around the clips...though the good suggestion above of using talc might have shown something.
So I'd be inclined to suggest that unless replaced fairly recently, new suction hoses and clips, for what they cost, could at least eliminate a possibility.
 
trthebees said:
So I'd be inclined to suggest that unless replaced fairly recently, new suction hoses and clips, for what they cost, could at least eliminate a possibility.
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I suggested proper fuel line clips. Their engineer, independently, has suggested them as well. He has replaced, at least some, the fuel line.
Fascadale said:
Thanks for your ongoing interest

The story so far...............................

We took the advice of the excellent John from Beta and put in a "Pigs Tail" as well as sorting the other joins on the return system. (Using top of the range clips)
Click to expand...
 
Sometimes any restriction in flow from tank is not obvious on a FULL tank my engine was perfectly happy but after 8hrs it was losing power as less gravity from head of diesel caused fuel starvation and maybe air was sucked in through hose joints also as the revs drop the lift pump is less effective this was many years ago when I first bought boat but it had me foxed for a while .
 
Are the connections to filter housing correct, as in flow direction arrows. Similar symptoms when my new engine was installed, took me ages to find fitter had put filter back to front, only found it when in desperation I started to take the fuel system apart starting at tank.
 
An update, and again thanks for the advice.

(the fuel tank was emptied and cleaned out at the start of last season so I'm reasonably confident that it was not a "debris in the tank" problem, but I have considered it. As you can see the tank is fibreglass and suffers more from sludge than debris)

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We first sought suggestions in Camaret, where the engine stopped as we entered the marina after the long motor at the end of the Biscay crossing. At the advice of John from Beta, and others we put a "Pig's tail" in the return pipe immediately beside the return from the injector rail.

We also discovered that a couple of the pipe/outlet joins could revolve although there was no sign of a leak.

Here is the "Pigs tail" and evidence of "proper clips"

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The next leg of our journey was Camaret to St Peter's Port: the engine worked perfectly.........happy days

St Peter's Port to Lowestoft demanded a long motor through the Goodwins and across the Thames. Fortunately I decided to test the engine a few miles off: it cut out when I dropped the revs. After leaving it for ten minutes it restarted and we made Lowestoft.

Lowestoft to Edinburgh and it did the same thing: perfect from about Newcastle to Leith, cut out as I slowed, restarted after a while allowing a very fast entrance to our harbour.

So it's back to the drawing board.

I'm convinced the problem is in the fuel delivery system so now that the boat is safely home I plan to take the belt and braces approach and examine every component along the line, tank, primary filter, pipework, secondary filter, banjos, lift pump, high pressure pump and injectors. Could be an expensive process.

It was not all doom and gloom though: some of the sailing was fantastic, goose winged up the north coast of Brittany for ten hours doing about 5 knots

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Some beautiful weather

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And plenty of food and drink

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Who says you cannot live well on a 26ft boat?
 
I'm an ensign tart.

Whatever goes better with the colour of the sky..................( quite a clever but totally unintentional pun)
.......................but lets not go there

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