Engine fuel mystery

Let's hope this is sorted sooner rather than later. I would still advocate going back to 5/16inch or 8mm copper with proper compression joints for all pipe-work apart from the connections to the engine.
This would have been far cheaper than hose in the first place as everything is available comparatively cheaply from your local hydraulics supplier.
 
Remove the fuel line at the diesel lift pump, close the valves at the fuel tanks and presurise the fuel lines using a small hand pump from the lift pump end, you will soon find any leak as you pressurise the system. If it leaks diesel it will suck air, I had a simular proplem. Using this method it is very easy to determine if a leak and hence air ingress is present.
 
I hate having pipe connections anywhere above the tank fuel level. If there is a leak it always lets air in, rather than letting fuel out. Also all those loops look like a nice air trap. I got rid of the fuel suction through the tank top, and have an outlet at the bottom, the primary filter is as low as it can be. I have seen several systems altered like this. I personally would not use flexible pipe and jubilee clips, all mine are hydraulic hose, you need the right fittings for the filters. Every connection is a potential problem, keep them to a minimum.

May not apply to you, but my only problem was with the two engine mounted filters. Although the first filter is under pressure from the lift pump, the last bleeder is on the injection pump side of the filter, when the filters started to get dirty the last bleeder let air in through a badly scored seat under the bleed screw, I could not see it, too close to the deckhead. The washer was aluminium, changed it to copper.
 
Beware of useing hydraulic hoses, they are not designed for diesel but hydraulic oil and can rot with diesel!
Always check not just copper washers but also the seating faces, had problem with brand new fuel tank and it was no more than a scratch on the surface, fibre washer cured that one.
Agree with comments on "jubilee" clips so double check them too.
I like non regulation semiclear pipe like you get in a pub for the beer, might be worth fitting a piece in temporary, you can see what is happening but not recommended for permanent use.
If you get really pissed off dont throw the engine away, I need that model for my digger!!!!!!
 
Dismantled completly and checked air breather/vents and they are clear.
Also noticed:
main infeed fuel pipe to pump,then out of pump 'into' secondry filter, 'out' of secondry filter to engine block fuel manifold (3 cylinder), then only one fuel return pipe with none return valve fitted.
Also tightened nut below the handle of three way valve.
Also check we have at least 7 boats all with same pipework sizes and same sized jubilee clips
all with no problems.
 
Copper pipe

I'd not recommend using copper pipe for diesel, from talking to a company that makes diesel bug killer and tests diesel and oils for the bug, copper will accelerate the bug. Just to check I googled this and apparently it also oxidises the fuel reducing its useful life if kept in contact with the copper pipe. Aero engines don't use copper for this reason and probably explains why the fuel pipes on my Volvo are all ally.

Good luck with your quest
 
Zephyr362 said:
I'd not recommend using copper pipe for diesel, from talking to a company that makes diesel bug killer and tests diesel and oils for the bug, copper will accelerate the bug. Just to check I googled this and apparently it also oxidises the fuel reducing its useful life if kept in contact with the copper pipe. Aero engines don't use copper for this reason and probably explains why the fuel pipes on my Volvo are all ally.

Good luck with your quest
Click to expand...
All I can find about copper is to do with biodiesel, completely different animal
Stu
 
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