Purge Valve
Purge Valve
The EVAP canister purge valve is located in the engine bay at the LH side of the engine intake manifold. The valve is held in position by a plastic clip which secures the inlet pipe of the purge valve to a bracket mounted at the rear of the engine compartment. On NAS vehicles with secondary air injection, the purge valve is fixed to a metal bracket together with the SAI vacuum solenoid valve; the purge valve is fixed to the bracket by two plastic clips.
A nylon pipe connects the outlet of the purge valve to the stub pipe on the plenum chamber via a short rubber hose. The connector to the plenum chamber is a quick-release type, plastic 90 degrees female elbow; the connection is covered by a rubber seal which is held in position on the port stub pipe.
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 of the engine bay. The service point is used by dealers for pressure testing using specialist nitrogen test equipment for localising the source of small 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.
Purge valve operation is controlled by the engine control module (ECM). The purge valve has a two-pin electrical connector which links to the ECM via the engine harness. Pin-1 of the connector is the power supply source from fuse 2 in the engine compartment fusebox, and pin-2 of the connector is the switched earth from the ECM (pulse width modulated (PWM) signal) which is used to control the purge valve operation time. Note that the harness connector for the purge valve is black, and must not be confused with the connector for the Secondary Air Injection vacuum solenoid valve which is grey.
When the purge valve is earthed by the ECM, the valve opens to allow hydrocarbons stored in the EVAP canister to be purged to the engine inlet manifold for combustion.
If the purge valve breaks or becomes stuck in the open or closed position, the EVAP system will cease to function and there are no default measures available. The ECM will store the fault in memory and illuminate the MIL warning lamp if the correct monitoring conditions have been achieved (i.e. valve status unchanged for 45 seconds after engine has been running for 15 minutes). If the purge valve is stuck in the open position, a rich airfuel mixture is likely to result at the intake manifold, this could cause the engine to misfire and the fuelling adaptions will change.
The following failure modes are possible:
^ Sticking valve
^ Valve blocked
^ Connector or harness wiring fault (open or short circuit)
^ Valve stuck open
If the purge valve malfunctions, the following fault codes may be stored in the ECM diagnostic memory, which can be retrieved using 'Testbook':
P-code Description
P0440 Purge valve not sealing
P0444 Purge valve open circuit
P0445 Purge valve short circuit to ground
P0443 Purge valve short circuit to battery voltage