Volvo 2040B - fuel problem diagnosis help please?

[PJSail]

Our totally reliable and (we think!) well maintained 1995 engine stopped suddenly 24 hours into a 30 hour leg off the Portugese coast.

We were low-ish on fuel but not empty and also feared that the sudden stop might be attributable to fishpot propeller wrap

Our immediate action just in case my calcs were wrong was to put in the spare 10 litres of diesel. The engine restarted and appeared fine in neutral. After sailing for a spell we restarted again and it performed fine for two hours before once again stopping abruptly.

Whilst still at sea I checked both the prefilter - clear fuel in glass bowl (from which I deduced that there was not a problem such as bad deposits/contamination with fuel) and then the engine fuel filter - which I discovered to be half empty and with a slight sound of suction when I loosened it.

Having got safely to port by combination of sailing and marina tow, I have carried out the following to trace the problem working from the engine back.

1) hand pump with fuel filter bleed opened - did not appear to work
2) detach fuel supply after prefilter at fuel pump - fuel flowed - due to siphon effect - and was clean- I collected a cupful to check
3) deduced problem was with fuel pump
4) removed fuel pump and could not detect suction by putting fingers over in/out and operating the manual pumping lever
5) dismantled fuel pump- no apparent problem with diaphragm/spring etc- cleaned off minor deposits from the two clear discs on both the in/out sides of top part of the pump
6) replaced main fuel filter (circa 170 hours since last)
7) bled through using manual fuel pump lever (though assume it might actually self bleed due to aforementioned siphon effect)

After bleeding through it is all starting and running fine and we are of course now very concerned that I have not actually found a definitive fault and that it may let us down again.

Any advice appreciated please.

 

[Heckler]

Our totally reliable and (we think!) well maintained 1995 engine stopped suddenly 24 hours into a 30 hour leg off the Portugese coast.

We were low-ish on fuel but not empty and also feared that the sudden stop might be attributable to fishpot propeller wrap

Our immediate action just in case my calcs were wrong was to put in the spare 10 litres of diesel. The engine restarted and appeared fine in neutral. After sailing for a spell we restarted again and it performed fine for two hours before once again stopping abruptly.

Whilst still at sea I checked both the prefilter - clear fuel in glass bowl (from which I deduced that there was not a problem such as bad deposits/contamination with fuel) and then the engine fuel filter - which I discovered to be half empty and with a slight sound of suction when I loosened it.

Having got safely to port by combination of sailing and marina tow, I have carried out the following to trace the problem working from the engine back.

1) hand pump with fuel filter bleed opened - did not appear to work
2) detach fuel supply after prefilter at fuel pump - fuel flowed - due to siphon effect - and was clean- I collected a cupful to check
3) deduced problem was with fuel pump
4) removed fuel pump and could not detect suction by putting fingers over in/out and operating the manual pumping lever
5) dismantled fuel pump- no apparent problem with diaphragm/spring etc- cleaned off minor deposits from the two clear discs on both the in/out sides of top part of the pump
6) replaced main fuel filter (circa 170 hours since last)
7) bled through using manual fuel pump lever (though assume it might actually self bleed due to aforementioned siphon effect)

After bleeding through it is all starting and running fine and we are of course now very concerned that I have not actually found a definitive fault and that it may let us down again.

Any advice appreciated please.

You might have found the prob with the fuel pump and deposits or you can check the stack pipe filter, there is usually a small gauze filter on the end. It could be getting clogged, then the bits drop off when you stop the engine and then reclog it after. while.
S

 

[paul-essex]

I would think it was a blocked filter and by replacing them you have solved the problem

 

[PJSail]

You might have found the prob with the fuel pump and deposits or you can check the stack pipe filter, there is usually a small gauze filter on the end. It could be getting clogged, then the bits drop off when you stop the engine and then reclog it after. while.
S

many thanks -afraid I don't know what the 'stack pipe' is ?

 

[Heckler]

many thanks -afraid I don't know what the 'stack pipe' is ?

its the pipe that goes in to your tank
S

 

[PJSail]

Duh!! I had worked that out since posting - will check those -twin linked tanks- tomorrow. Many thanks for counsel - much appreciated
P

 

[VicS]

Duh!! I had worked that out since posting - will check those -twin linked tanks- tomorrow. Many thanks for counsel - much appreciated
P

Any drain(s) on the bottom of the tank(s) that would enable you to drain off any water and sludge that has accumulated ?

 

[PJSail]

Not that I can see - I have one small top access which can be used for a dipstick or pump out and then the plates circa 150mm with all the connections of pipes in and out, both of which look like they were assembled before 'squeezing' the tanks into position in the cockpit locker. However the two tanks are interconnected at low level so thanks for the prompt so will check if I can use that connection for drainage purposes ! Fortunately little in tanks at present so should be feasible and definitely worth doing before refilling.
P

 

[nigelmercier]

... you can check the stack pipe filter, there is usually a small gauze filter on the end...

I have seen such filters on lawnmowers, but on a boat? IMO this is the last place you want a filter.

 

[david_bagshaw]

Would suggest nothing wrong with lift pump as manual lever doesnt work if cam is at high point.

does tank up take go fare enough down towards bottom of tank, may bee some air got in stopping engine.

 

[michael_w]

Sounds like there is some rubbish floating around in the tank and it's being sucked into the intake pipe at irregular intervals, leading to the fuel starvation. As soon as you stop the engine the rubbish falls to the bottom of the tank till next time!

I've had this twice. Once with my elderly Landrover (never found the culprit, so fiited a baloon filter on the pick up) and on my boat, which after much investigation, fuel polishing etc, turned out to be a plastic washer from a fuel additive bottle.

 

[PJSail]

Thanks David

Am aware ref cam so jog the engine around until it works and also when had it out pressed in the 'foot' that sits on the cam. still could not feel suction with fingers over the two holes.

Anyway update is that I have realised that my twin linked tanks are different depths and the fuel intake takes from both and I had the valves on both open (have had since buying the boat 4 years ago). believe what happened was used fuel till reached below the level of the intake in the shallower, outboard tank so that one was then sucking air whilst the other was still potentially in a position to draw fuel from the deeper tank. Drained both today and there is a further 20 odd litres from the deeper tank after the draw from the upper runs dry- but you can only get it by turning off the valve to the upper tank.

Have also managed to see inside one tank and there is no gauze filter and very little sludge/dirt apparent and the intake seems to stop about 20mm up from the base of the tank.

So in future I shall always either leave the upper tank valved off OR regard the lower tank as a reserve and keep it valved off until I know that I need it -( or run dry!)

does this make sense?

thanks to you and others for helpful responses.

PJ