Gravity feed fuel.

[fisherman]

Can any engineer tell me if a ford 2720 will run on fuel gravity fed to the injector pump, or do you have to have lift pump pressure?

 

[BarryH]

Can't see it working myself and what are you going to do with the fuel return? That won't flow up hill..........

 

[savageseadog]

Gravity feed on its own is fine, as long as you can prime the fuel system in some way.

 

[fisherman]

I have for a long time thought to have a header tank to run the engine with a gravity feed. The header tank, capacity about 25lts, would be fed from the lift pump, with an overflow back to the main tank. In the bottom of the header tank would be a sump and drain for contaminants, nice and accessible. The header tank would have a filler so it could be filled from a can in an emergency.

 

[andy_wilson]

Course it will. The lift pump is purely that, a low pressure pump to provide airless diesel to the high pressure side that runs at a far higher pressure to feed the injectors.

There will be plenty spare pressure in the return to lift the fuel to any height you are going to find on a leisure boat. Crack a union in a return pipe and watch it squirt!

Incidentally it used to be a standard practice for commercial vessels to have a gravity fed day tank. Fuel from the main tank would be lifted to it daily (as consumption is fairly constant) and logged.

Should be no problem at all.

 

[fisherman]

Thanks, that's encouraging. I was going to leave the return to the main tank, but if the header tank was being used as an emergency supply filled from a can a lot of fuel would end up back in the main tank, so will rig the return to the header tank as well.

 

[savageseadog]

As point of interest most of the peugeot/Citroen XUD engines use a suction feed system, no lift pump, no gravity either. The fuel is drawn up by the injection pump (which is why so many of them have fuel starvation/ intermittent running problems due to faulty filter housings/pipework etc) They use a squeezy bulb to prime/vent the fuel system. Suggest you use a filter separator with a built in pump to prime owing to boat fire risks. The return is pressurised so no problem there.
Gravity feed will be no problem otherwise.

 

[fisherman]

I've snit a hag. In line injector pump needs pressure from the lift pump, which delivers at 4or 5 psi. Header tank would need to be about 10 ft up. Water is .445 psi per ft.