Disassembly; Inspection; Reassembly - Toro TC 1000 Service Manual

Fuel Cap Operation (cont'd)
3. Pressure passes into the top of the gas cap
and is emitted to the atmosphere through the
slits in the threads of the gas cap.
When a vacuum occurs within the tank, the
following occurs: See Fig. 45.
UMBRELLA VALVE
Figure 45
1. Atmospheric pressure enters the top of the
gas cap through the slits in the gas cap
threads.
2. Because a vacuum in the tank means that
higher pressure is present outside the tank
than within, the higher pressure passes down
the stem of the umbrella valve and forces the
stem orifice open.
3. The higher pressure
passes through the
packing orifice and enters the fuel tank
thereby equalizing the pressure.
Fuel Cap Disassembly
1. Remove the fuel cap from the tank.
2. Pry the gasket, holder and breather valve out
of the tank cap. See Fig 46.
Figure 46
3. Clean these parts thoroughly.
Fuel Cap Inspection
1. It is important that the fuel cap properly vents
the tank. Check to ensure that the packing
orifice is unobstructed.
2. Check the two small pressure outlet holes in
the valve holder to ensure that they are open.
3. The stem of the umbrella valve allows air into
the tank to compensate for the fuel being
used by the engine. Ensure that it will open
and close by holding the flat end lengthwise
between your thumbs and squeezing. See
Fig. 47.
Figure 47
4. Clean all fuel cap parts thoroughly.
Fuel Cap Reassembly
1. Position the holder inside the gasket then
screw this assembly into the fuel cap until it is
fully seated in the top of the fuel cap.
2. Reinstall the cap on the fuel tank.