Cub Cadet T65 Series - Manual (Page 46)

T65 Series Vertical Shaft Engines
40
Fuel tank vent
The fuel tank vent performs the important task of allow-
ing air into the fuel tank. As fuel is being used by the
engine, the fuel level in the tank drops. The dropping fuel
level then creates a vacuum in the tank. If the fuel tank
could not allow air through the vent, the vacuum would
prevent the fuel from getting to the carburetor.
The tank is vented through the cap. See Figure 4.6.
NOTE: This is a charcoal canister fuel cap. If the
vent is not functioning, the whole fuel cap
must be replaced.
To test the cap vent:
1. Drain the fuel out of the fuel tank into an approved
container.
2. Attach a hand-pumped vacuum/pressure tester to
the fuel barb on the fuel tank. See Figure 4.7.
3. Attempt to pull a vacuum on the fuel tank with the
fuel cap in place.
4. Attempt to pressurize the fuel tank with the fuel cap
in place.
NOTE: The tank should not hold any pressure nor
any vacuum.
• Replace the cap if either pressure or vacuum
builds using the hand-pump tester.
• A cap that maintains pressure will cause the
engine to run rich as the fuel in the tank heats
and expands, forcing it’s way past the float
valve in the carburetor.
• A cap that maintains vacuum will cause the
engine to run lean as the fuel is depleted and
no air comes in to replace it.
• The two conditions may both be present, but
the symptoms vary with fuel, fuel level, and
operating conditions.
• Usually presents as a “Runs and quits” sce-
nario.
Figure 4.6
Vent hole
Figure 4.7
Hand-pump vacuum
/pressure tester