In a message dated 97-03-14 11:56:24 EST, you write:
<< First, forgive me for not completely understanding the inner workings of
these pumps. We have two types of electric fuel pumps from which to
choose for our LBCs: the traditional Skinners Union type with contact
breakers either in positive ground (earth) or negative ground and the
electronic breakerless variety.
Now, my questions: in the event of pump failure, would another pump
mounted inline, either pushing or pulling, move fuel through the
disabled pump and thus keep the fuel system operative? Would the
non-functioning pump's diaphragm effectively act as a check valve and
not allow fuel through? Has anyone tried this?
I haven't actually tried this, but I can explain how a fuel pump works.
A fuel pump consists of a fuel chamber, spring loaded diaphram, inlet check
valve, outlet check valve, switch (points or solid state), and a solenoid.
To start the description, assume the fuel chamber is empty. At this time, the
switch is closed, energizing the solenoid, which pulls the diaphram back,
against the spring pressure. This creates a suction which closes the outlet
valve, opens the inlet valve, and draws fuel into the chamber. When the
diaphram is fully retracted, the switch opens, allowing the spring to push
the diaphram forward. This creates a pressure which closes the inlet valve,
opens the outlet valve, and pushes fuel to the carbs. The needle valves in
the carbs control the rate of discharge. When the diaphram is in the full
forward position, ie, the fuel is discharged, the switch closes, repeating
As you can see, both the inlet and the outlet valves operate to allow fuel to
flow toward the carbs. Unless the diaphram presses against the inlet valve in
the full discharge position, or otherwise creates a restriction, it should be
possible to pull (or push) fuel throught it with another pump.
Of course, your question was not is it possible, but does it work! I am
looking forward to an answer from someone who knows, because I have
considered this myself. Maybe someday I will make a test.
I hope this is of some help.