Specifications

19
SECTION 7. IMPULSE FUEL PUMP
IMPULSE FUEL PUMP. This pump is mounted onto
the carburetor inlet and has connections from the
fuel supply and also a pulse line to the engine crankcase.
CAUTION: IN ORDER FOR THE PUMP TO OPERATE
SATISFACTORILY THE CORRECT OIL LEVEL IN
THE CRANKCASE MUST BE MAINTAINED. TOO
MUCH OIL WILL ADVERSELY EFFECT THE PUMPS
OPERATION.
It is operated by changing pressure created by the
engine piston movement and transmitted to the pump
through a pulse line. The increasing and decreasing
pressures acting on the diaphragm and flap valves
lift fuel from the fuel tank to the carburetor of the
engine.
To service, separate the pump by removing the four
(4) screws. Clean all new parts with a solvent and
install a new kit which consists of coil springs, gaskets
and diaphragms.
The diaphragms must be installed against the center
body with the gaskets against the outside covers.
The parts are designed so they cannot be misassembled
without damage.
To test the unit, assemble the carburetor to the engine,
leaving the pump off. Connect gravity fuel feed supply
to the carburetor. With the pulse line connected to
the pump and engine running, a definite flow should
result.
If the flow is erratic or intermittent, the pump needs
repair or replacement.
CARBURETOR FITTING
VALVE OPEN
DIAPHRAGM
VALVE CLOSED
PULSE LINE
TO CRANKCASE
FUEL SUPPLY
AIR BLEED
VALVE
CLOSED
VALVE
OPEN
FILTER
ATMOSPHERIC
VENT
CRANKCASE PRESSURE CRANKCASE SUCTION AND Ü SUCTION FUEL FLOW
FLOW DIRECTION DIRECTION
Ô ATMOSPHERIC PRESSURE Ô ATMOSPHERIC PRESSURE Ô ATMOSPHERIC PRESSURE
ACTING ON DAMPING ACTING ON DAMPING CAUSED FUEL FLOW
DIAPHRAGM DIAPHRAGM
ÜFUEL FLOW
±
±
FOUR SCREWS INTO
BACKSIDE OF PLATE
TO BACKSIDE
OF PLATE
WHEN ASSEMBLED
THIS SIDE FACES INTO
CONCAVE CAVITY OF
ABOVE ASSEMBLY
SPRING IN
HOLE CAVITY
BUTTON WITH SPRING
TYPE I
PREVIOUS STYLE
TYPE I
NEW STYLE
TYPE II
The new style pump (TYPE II) will replace older (TYPE
I) pumps. An assembly kit is available with instructions
and all the parts needed to convert to the new style.
If a complete replacement of an old style is not necessary,
a repair kit is still available.