Cub Cadet MTD P71 Series - Manual (Page 47)

F UEL S YSTEM AND G OVERNOR
41
Evaporative (EVAP) emissions system
NOTE: All gasoline powered engines built on or after Jan-
uary 1, 2012 must meet Phase III emissions.
Phase III emissions requires that the engine have
an evaporative emissions system to limit the
amount of fuel vapors that escape into the atmo-
sphere.
NOTE: Also all fuel caps must be tethered to the fuel tank
as part of the EPA tier III emissions. A broken
tether on the fuel cap must be repaired before the
unit can be put back into service.
The EVAP system consists of:
• A charcoal canister
• The fuel tank and cap
• Vacuum lines
This system operates as follows:
1. The gasoline evaporates, letting off vapors.
2. The vapors exit the fuel tank through a vacuum hose.
3. The vapors are routed through the charcoal canister.
See Figure 4.9.
4. The activated charcoal inside the canister absorbs
the hydrocarbons allowing the air to pass through
and out to the atmosphere.
5. When the engine is running, the vacuum between the
air filter and the carburetor is used to draw the vapors
out of the charcoal canister, temporarily enriching the
fuel/air mixture, and is used in the combustion pro-
cess.
6. When the engine is running, the vacuum inside the
carburetor insulator is used to draw the vapors out of
the charcoal canister, temporarily enriching the fuel/
air mixture, and is used in the combustion process.
See Figure 4.10.
Figure 4.8
Charcoal canister
Vacuum line
Purge line
Fuel
Tank
AIR
Engine
Char
coal
Canist
er
Figure 4.9
Fuel
Tank
AIR
Engine
Char
coal
Canist
er
Figure 4.10