Husqvarna K770 Workshop Manual page 35

6.5.5 Function tank venting
The tank has a check valve that let air enter the tank,
but prevents fuel from running out. The filter lets air
through slowly.
6.5.6 Tank air flow fault indication
If the tank air flow is blocked and the engine is running,
the tank will have low pressure. This decreases fuel
supply and the power. When you open the fuel tank cap
you will hear the sound of air suction. A clogged filter
must not be blown clean, but replaced.
6.5.7 To remove the tank air flow filter
1. Lift the check valve and then the filter with a pair of
pliers.
6.5.8 Function air purge
1
The air purge removes air from the fuel chamber of the
carburetor and fills it with fuel.
701 - 002 -
2
Hose 1 is connected to the carburetor. The pump
causes a vacuum in the fuel chamber and fuel is pulled
into it. When the fuel chamber has been fully filled,
unwanted fuel is pushed to the tank through return hose
2. This means that the fuel level in the carburetor does
not get too high.
6.5.9 To examine the air purge
To examine the air purge, use Husqvarna test
instrument for fuel lines and check valves. See
tools overview on page 13
Press the bladder of the pump. It must be filled with fuel.
If it is not filled with fuel, the pump must be examined.
1. Connect the test instrument to the hose from the air
purge.
2. Set the test instrument for vacuum test.
3. Pump up a vacuum to 0.3–0.5 bar using the air
purge – not the tester.
If this can be done, the pump and hose connection are
not damaged. You must then look for the fault in the
other components of the fuel system.
Servicing
Repair and servicing - 35