Mallory Ignition ACCEL Digital Fuel Injection Engine Management System 74030 - Manual (Page 18)

16
ACCEL/DFI
DUAL FUEL TANKS
It is important to note that for vehicles with two fuel tanks
and/or a class “A” RV, it is highly recommended that a
boost pump be installed in each tank and feed though a
multi-port switching valve, especially when operating in
hot climates. Boost pumps used on such vehicles as a 1985
Ford F-250 5.0L EFI will work well for this type of applica-
tion. The switching valve from a 1984 Ford Diesel or a 1986
Chevrolet C-10 (305 CID) will work well in dual tank appli-
cations. Dual tank equipped vehicles must be plumbed to
return excess fuel to the tank which is supplying fuel to the
EFI system to avoid tank overflow problems. The remotely-
activated dual tank three-way valves described above will
work well in these applications.
A NOTE TO THE INSTALLER
There seems to be a misunderstanding with some people
that a fuel pump “produces pressure”. This is not accurate.
What actually happens is the pump produces fuel flow at a
given system pressure which is dictated by the pressure
regulator. The pressure regulator has a spring which is
preset to provide a certain system pressure, i.e. 45 PSI. The
regulator opens as the pressure in the fuel line increases
due to the flow of fuel provided by the pump.
As the pressure drops, due to bypassing of fuel to the tank,
the regulator closes at a pressure of 45 PSI (this pressure is
variable on adjustable regulators). This process will begin
again as pressure raises. Therefore, the pressure regulator is
a dynamic modulating device which always tries to seek its
preset pressure.