The dual fuel pump is also an issue for me. I overhauld the complete system on my 420SEL last year. My 300SE only has one pump but the steup is similar.

Fuel is gravity fed from the tank to the pump. From there is goes into the bottom pump and through the check valve to the upper pump and through its check valve to the filter and on to the CIS injection system. Attached to the pump is a fuel accumulator to keep the supply side pressurized and in case the internal diaphram ruptures, which is spring loaded, a return line to the 1st pump supply hose from the tank.

The reasons there are two pumps is the V8's require higher fuel pressure than the L6's, and higher fuel volume. The latter doesn't make sense because they are in series rather than parallel or one that is a higher volume pump.

__________________
Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.