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ABS Speed Sensor
Air Flow Meter / Sensor
Air Intake Pressure Sensor
Alternator Current and Voltage
Amplifier Earth
Camshaft Sensor
Carbon Canister Solenoid Valve
Crankshaft sensor
Coolant Temperature sensor
Diesel Glow Plugs
Digital ECM to Ignition Amplifier Signal
Distributor Pickup
Dual Trace
Electronic Fuel Pump
Exhaust Gas Recirculation
Idle Speed Control Valve
Injectors
Knock Sensor
Lambda Sensor
MAP Sensor
Primary
Relative Compression
Secondary
Supercharger
Throttle
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Carbon Canister Solenoid Valve Diagnostics

This canister contains active charcoal or active carbon granules.

Most evaporation control systems reduce the emission of fuel vapour during the time the vehicle is idling in traffic, or parked in strong sunshine by absorbing the vapour fumes into the carbon canister.

Once the engine is at its normal operating temperature the stored hydrocarbons are released into the inlet manifold where they become part of the combustible Air/Fuel mixture.

The control for allowing the hydrocarbons to be released into the inlet manifold through a cut off valve, can be achieved electrically or by vacuum: the operating principal is the same for both.

The electronic solenoid is controlled by the Electronic Control Module (ECM) by switching the earth path to ground under specified conditions. The purge valve/carbon canister has a 12 volt supply and its switching can be seen in the example waveform.

Technical Information

Fuel evaporation can be a serious source of atmospheric pollution from the hydrocarbon fuel stored within the tank. For this reason the tank has now become a sealed unit and a breather pipe allows fumes to collect within a canister, normally located in the engine compartment. This canister contains active charcoal or active carbon granules.

Most evaporation control systems reduce the emission of fuel vapour during the time the vehicle is idling in traffic, is stationary or parked in strong sunshine, by absorbing the vapour fumes into the carbon canister. Once the engine is at its normal operating temperature the stored hydrocarbons are released into the inlet manifold where they become part of the combustible Air/Fuel mixture.

The control for allowing the hydrocarbons to be released into the inlet manifold through a cut off valve, can be achieved electrically or by vacuum: the operating principal is the same for both.

The electronic solenoid will be controlled by the ECM. With the engine switched off or at idle there will be no vacuum signal in the cut off diaphragm chamber so the vapour fumes in the canister are prevented from being released into the inlet manifold. With the engine running above idle there will be a relatively high vacuum in the signal pipe.

This causes the vacuum cut off valve to lift off its seat and allow fresh air to be drawn into the bottom of the canister through the central tube. The air is then spread over the bottom of the canister and rises through the canister purging (pushing out) the hydrocarbon vapour through the cut off valve into the inlet manifold.




Here we have a cross section of a carbon canister, with the vacuum valve in the closed position.