Onan CCK Service Manual

PULSATING DIAPHRAGM GASOLINE
FUEL PUMP
Pulsating diaphragm fuel pumps use a combination
crankcase and spring pressure to work a diaphragm
thus pumping fuel. This pump may be mounted to the
side of the carburetor or, in some tractor applications,
on the upper right hand corner of the blower housing.
On the downstroke of the engine piston, when the
crankcase pressure is greatest, the pump diaphragm
is forced back against the diaphragm spring com¬
pressing it and drawing fuel into the pump intake
chamber. The fuel then passes through the intake
reed valve into the output chamber side of the pump.
On the compression stroke, when crankcase pressure
is the lowest, the diaphragm spring forces the
diaphragm out pushing fuel through the pump output
reed valve into the output chamber and into the fuel
line.
Servicing Fuel Pump
1. R emove vacuum and luel lines. Inspect lines for
wear, cracking, etc.
2. Scribe two lines (one each on opposite ends of
pump) across pump parts. This will ensure cor¬
rect alignment of pump parts with each other and
carburetor when pump is reassembled.
3. Remove fuel pump attaching screws.
4. Holding pump, carefully pull sectionsof the pump
apart. The diaphragm, plunger, return spring and
plate, pump body and gaskets will now be loose.
5. Check parts for wear and damage. Replace with
new parts where necessary.
6. The air bleed hole in pump base must be unclogg¬
ed to allow unrestricted movement of diaphragm.
P^aijxion^T a clogged diaphragm air bleed hole
^ can cause diaphragm wear and seat
damage white inhibiting pump operation.
7. Replace gaskets and reassemble pump as shown
in Figure.
8. install pump and replace lines. Makesunefuei line
clamps are replaced on fuel line.
warning | Use care when reassembling and
reinstalling the pump. Improper
parts alignment ormisconnected fuel lines may result
in leaking fuel, creating a serious fire hazard.
PUMP COVER GASKET VALVE GASKET DIAPHRAGM
i 1 lit DUMP PI ATC
PULSATING DIAPHRAGM FUEL PUMP
29

Onan CCK Specifications

General

Cylinders	2
Ignition System	Battery ignition
Fuel Type	Gasoline
Cooling System	Air-cooled
Fuel System	Carburetor
Starter	Electric
Governor	Mechanical
Max RPM	1800 RPM
Engine Type	4-cycle
Bore and Stroke	3.25 x 3.625 inches (82.55 x 92.08 mm)