Husqvarna K 760 Workshop Manual page 21

9
A
1
3
21
FUEL SYSTEM
B
2
Non-return valve – functional test
Connect the non return valve to pressure tester 501 56 27-01.
Note: Never expose the non return valve to a high pressure (compressed air)!
Test the non return valve by first blowing in the direction towards the tank.
The air should pass without a build up of pressure.
Blow in the direction towards the filter. The non return valve should stop a
pressure of approximately 3–6 psi/20–40 kPa. At a higher pressure the non
return valve opens.
Air purge
The pump has a suction function and is connected to the carburettor's fuel
chamber. The air purge empties the fuel chamber of any air and tops up the
fuel chamber with fuel. With continued pumping, any excess fuel is returned
to the tank.
Function
Hose A is connected to the carburettor. The pump creates a vacuum in the
fuel chamber and fuel is drawn into it. When the fuel chamber has been fully
filled excess fuel is pumped to the tank via return hose B.
The design entails that the amount of fuel in the carburettor can never be
too much regardless of the number of pushes on the air purge bulb.
Functional test
Test the pump by depressing the air purge bulb several times. This should
then fill with fuel that is visible through the air purge bulb.
If the air purge bulb does not fill with fuel, the pump itself must be
examined in order to determine if the fault lies there.
Dismantle the carburettor and connect the test instrument 501 56 27-01 to
the pump's carburettor hose (A as depicted at the top). Set the test instrument
for vacuum measurement. Pump to a vacuum of around 30–50 kPa using air
purge – not the test instrument. The pump is intact if this can be
achieved and the fault must then be sought in the other components of the
fuel system.
Dismantling/assembly
1. Detach return hose (B) from the pump.
2. Press the snap locks together and push the pump out.
Exercise care when assembling. Push the hoses fully on to their connectors to
avoid fuel leakage.
3. Note that the transparent carburettor hose must be positioned in front of
the return hose. Behind the black return hose in the illustration.