what does that canister do
The ‘70s Shake-up – ADR 27A
In mid 1976, the federal government introduced ADR (Australian Design Rule) 27A in an attempt to reduce car emissions.
ADR 27A requires that each car built from July 1st, 1976 be fitted with a positive crankcase ventilation system, an evaporative emission control system and an exhaust gas recirculation system.
So how does ADR 27A related equipment reduce emissions, you ask? Well, the PCV system reduces the amount of unburned crankcase hydrocarbons that are released to atmosphere by redirecting these hydrocarbons into the combustion chambers. Vehicles employ a system that draws fresh air from the air cleaner assembly into the crankcase via a passage in the oil filler cap. This fresh air mixes with crankcase vapours and is drawn into the combustion chambers through a PCV valve that connects to the carburettor throttle body. For efficient operation, the PCV valve must function properly and the crankcase must be sealed (no leaks at the dipstick or oil filler).
The next part of the ADR 27A arsenal is an evaporative emission control system; approximately 20 percent of all hydrocarbon emissions are caused by evaporative losses from the fuel tank. Vehicles employ an ‘absorption-regeneration’ system which temporarily stores evaporated fuel vapour inside a charcoal canister.
EVAPORATIVE EMISSION CONTROL
The Evaporative Emission Control System (EECS) controls fuel vapours which would normally escape from the fuel tank to be consumed in the combustion process. The EECS used on VS Series Models is the charcoal canister storage method. This method transfers fuel vapour from the fuel tank to an activated carbon (charcoal) storage canister to hold vapours when the vehicle is not operating. When the engine is running, the fuel vapour is purged from the carbon element by intake air flow and consumed in the normal combustion process. The fuel tank cap is not vented to atmosphere, but is fitted with a valve to allow both pressure and vacuum relief.
The canister is a three port design. The canister is located in the engine compartment between the radiator and the battery, mounted to the front end support panel.The fuel vapour is absorbed by the charcoal in the canister. When the engine is running at idle speed, air is drawn into the canister through the atmospheric port at the top of the canister assembly. The air mixes with the vapour and the mixture is drawn into the intake manifold via the canister purge line.
The uppermost port on the canister is controlled by a PCM controlled purge solenoid valve. The solenoid valve controls the manifold vacuum signal from the throttle body. The port below the canister purge port is the vapour inlet port from the fuel tank. The single off centre port is open to the atmosphere. This system has a remote mounted canister purge control solenoid valve. The PCM operates this solenoid valve to control vacuum to the canister. Under cold engine conditions, the solenoid valve is turned "OFF" by the PCM, which blocks vacuum to the canister and prevents purge. The PCM turns "ON" the solenoid valve and allows purge:
. When the engine coolant temperature is less than 80 C, 3 minutes and 15 seconds after engine start.
. When the engine coolant temperature is greater than 80 C, 5 minutes after engine start.
. Engine is not in Decel Fuel Cutoff Mode and the throttle opening is less than 92%.
. Engine is in Closed Loop Fuel Mode.
The canister cannot be repaired, and is serviced only as an assembly. Periodically check the canister at the time or distance intervals specified in the VS Series Owner's Handbook.
