EVAP (Charcoal) Canister

EVAP (charcoal) Canister





The EVAP canister is mounted on a bracket fitted beneath the vehicle on the RH side of the chassis. The EVAP canister ports face towards the front of the vehicle. The EVAP canister has inscriptions next to each port for identification of the 'purge', 'tank' and 'air' connections.

The purge line from the EVAP canister is connected to the back of the inlet manifold plenum, after the throttle body via a purge valve. The pipe between the EVAP canister and the purge valve is routed over the transmission and into the LH side of the engine bay. The pipe clips to the purge port on the EVAP canister by means of a straight quick-fit connector and the connection is covered by a rubber seal which is held in position on the port stub pipe.

The vent line from the fuel tank to the EVAP canister connects to the vent port on the canister by means of an elbowed quick-fit connector. The line passes along the chassis behind the EVAP canister and terminates in a straight female quick-fit connector to the fuel vent line at the fuel filler.

The plastic pipe to the atmosphere vent line connects to the port on the EVAP canister by means of a short rubber hose and metal band clips. The atmosphere end of the plastic pipe terminates in a quick fit connector to the pipe leading to the CVS unit on NAS vehicles with vacuum type, EVAP system leak detection and two snorkel tubes situated behind the engine at the bulkhead on ROW vehicles. The bore of the plastic breather pipe is larger on NAS vehicles than on ROW vehicles.

For NAS vehicles with positive pressure, EVAP system leak detection capability, the atmosphere vent line from the EVAP canister connects to a port on the fuel leak detection pump via a short, large bore hose which is secured to the component ports by crimped metal clips at each end. A large bore plastic hose from the top of the leak detection pump is routed to the RH side of the engine bay where it connects to an air filter canister. Under normal operating conditions (when the fuel leak detection solenoid valve is not energised), the EVAP canister is able to take in clean air via the air filter, through the pipework and past the open solenoid valve to allow normal purge operation to take place and release any build up of EVAP system pressure to atmosphere.

The EVAP system pipes are clipped at various points along the pipe runs and tied together with tie straps at suitable points along the runs.

The NAS and ROW EVAP canisters are of similar appearance, but use charcoal of different consistency. The ROW vehicles use granular charcoal of 11 bwc (butane working capacity) and NAS vehicles use pelletised charcoal with a higher absorption capacity of 15 bwc. All canisters are of rectangular shape and have capacities of 1.8 litres (3 1/8 imp. pts) with purge foam retention.