I would have said "No". Its a diaphragm pump with check valves in and out. Are you sure it will flow?
well if it flows toward the engine but not the other way it would then flow through right? .....anyone know for sure?
Yes. I had one on my last boat. Also when my tank is full on this boat the level is higher then the engine and it does self bleed with gravity.
If the lift pumps fails, with a leak in the diaphragm the backup electric could flood the crankcase with diesel.
JohnP
Yes. I had one on my last boat. Also when my tank is full on this boat the level is higher then the engine and it does self bleed with gravity.
I have a different engine, but that is what I do and it seems to work just fine............... Wouldn't it be enough to simply fill the filter and let the lift pump do its job?............
The inlet check valve will open from either a vacuum applied downstream by the diaphragm or by pressure applied upstream by an external pump.
Bob
I just read the section on the FL120s fuel lift pump in the Ford service manual for this engine which is on the Grand Banks forum. It would appear that it is NOT a flow-through pump. There are spring-loaded valves on both the intake AND the outlet side of the pump. The inlet valve is opened under vacuum from the movement of the pump's diaphragm.
When the chamber is full the pressure from the diaphragm against the fuel opens the spring-loaded outlet valve while at the same time the spring-loaded inlet valve closes.
When the pump is not developing alternatiing vacuum and pressure from the action of the diaphragm-- in other words when the engine is not turning over--- BOTH the inlet and outlet valves are closed under spring pressure.
This is obviously why the people I know who have installed an electric auxiliary pump on their FL120s plumbed around the mechanical lift pump. Priming the fuel system using the electrical pump without the engine turning over means the inlet and outlet valves on the mechanical pump will be closed.
If the diaphragm fails with the engine running, the inlet and outlet valves will not open since there is no pressure available from the diaphragm to open them. So the auxiiary electric pump must be able to send fuel to the injection pump around the mechanical pump, not through it.
Thanks Marin. Now that you explained it i can understand that when the engine is not running the presure on the check vbalve wont open it because the outlet side check valve is closed. If the pumpos valves are worn it may leak through but it would likely have to be really old. These thread are a cornicopia of information
One of the reasons I'm doing this is to help flush my Racors. By having a shut-off valve after the filter, I can run the pump and open the Racor drain, flushing out the crud without having to open the filter or worry about air getting in the system.