V 3500 P/U 4WD V8-350 5.7L VIN M 4-bbl (1987)
Evaporative Emission Control Canister: Description and Operation
Auxiliary Canister
Fig. 60 Auxiliary charcoal canister
The auxiliary canister (ACC), Fig. 60, is added to some systems with enlarged fuel capacity (dual or optional fuel tanks) to increase the vapor storage
capacity of the EEC system. The auxiliary canister is used in conjunction with a closed bottom main canister and connected to the main canister purge air
inlet. The auxiliary canister stores vapor overflow from the main canister, and during purging, air is drawn into the system through the auxiliary canister
vent.