Evaporative Emission System Control Components (From 99MY)
EVAP Canister:
The EVAP canister is mounted beneath the vehicle on the RH side of the chassis, and is held in position by means of a dedicated bracket. The ports of the canister face towards the rear of the vehicle. The EVAP canister has moulded 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 inlet manifold after the throttle body via a purge valve. The line between the EVAP canister and the purge valve is routed over the transmission and into the LH side of the engine bay where it terminates in a quick-fit connector which locates to a connector on the line leading to the purge valve. The pipe clips to the purge port on the EVAP canister by means of an elbowed quick-fit connector.
The vent line from the fuel tank to the EVAP canister connects to the vent port on the canister by means of a straight quick-fit connector. The vent line terminates in a quick-fit connector at the fuel filler.
The nylon pipe to the air 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 pipe terminates in a quick-fit connector to the pipe leading to the CVS unit on NAS vehicles and a snorkel tube situated behind the engine at the bulkhead on ROW vehicles. The bore of the nylon breather pipe used on NAS vehicles is larger than that used on ROW vehicles.
The 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 charcoal 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 pelletized charcoal with a higher absorption capacity of 15 bwc. All canisters are of rectangular shape and have purge foam retention.
Purge Valve:
The canister purge valve is located at the left hand side of the engine bay.
A nylon (santoprene overmoulded) pipe connects the outlet side of the purge valve to the stub pipe on the plenum chamber. The connector to the plenum chamber stub pipe is a quick-release type, plastic go°female elbow; the hose is a push fit onto a stub at the connector elbow. A short rubber stub hose is connected between the purge valve outlet and the nylon pipe to the plenum chamber. A connector insert is used to mate the rubber stub hose to the nylon pipe and is secured with crimped metal clips. A similar short stub hose is connected between the inlet side of the purge valve and a short nylon pipe to the service port. The nylon pipe is a push fit on the outlet stub pipe of the service port and a connector insert mates the nylon pipe to the rubber hose going to the inlet side of the purge valve. Crimped metal band clips secure the rubber stub hose at the purge valve port and the connector to the nylon pipe. A nylon pipe connects from the inlet side of the service port to a quick-fit connector that mates to the purge pipe leading to the EVAP canister; the nylon pipe connection to the service port inlet is a push-fit.
A service port is connected in line between the EVAP canister and the inlet side of the purge valve and is rated at 1 psi maximum regulated pressure. The service port must be mounted horizontally and is located close to the bulkhead at the rear left hand side of the engine bay. The service port is used for pressure testing using specialist nitrogen test equipment for localizing the source of leaks.
The purge valve has a plastic housing, and a directional arrow is moulded onto the side of the casing to indicate the direction of flow. The head of the arrow points to the outlet side of the valve which connects to the plenum chamber. The valve has a two-pin electrical connector which links to the engine management system ECM via the engine harness.
Fuel vapor separator
The fuel vapor separator is located under the right rear wheel arch next to the filler neck and protected by the wheel arch lining. The connections to the separator unit are quick release devices at the end of the flexible hoses which connect the fuel tank to the inlet side of the separator and the outlet of the separator to the evaporation vent line.
Canister Vent Solenoid (CVS) Unit - (NAS Only):
The CVS unit is mounted at the rear right hand side of the engine bay on a slide-on bracket. The vent pipe from the EVAP canister is connected to a stub pipe on the CVS unit via a short rubber hose. The rubber hose is connected to the CVS unit and plastic pipe by two metal band clips. A two-pin connector links to the engine management ECM via the engine harness for solenoid control. One wire is for the voltage feed, the other is the valve drive line to the ECM. The solenoid is operated when the ECM grounds the circuit.
Fuel Tank Pressure Sensor - (NAS Only):
A fuel tank pressure sensor is fitted to NAS vehicles in the top flange of the fuel pump sender unit and is not removable.
The pressure sensor is basically a piezo-resistive sensor element with associated circuitry for signal amplification and temperature compensation. The active surface is exposed to ambient pressure by an opening in the cap and by the reference port. It is protected from humidity by a silicon gel. The tank pressure is fed up to a pressure port at the rear side of the diaphragm.