GM S-Series Pick-ups and SUV's 1994-1999 Repair Guide

Evaporative Canister

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See Figures 1 through 4



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Fig. Fig. 1: Example of a common evaporative canister and hose assembly-6-cylinder engine



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Fig. Fig. 2: Common evaporative emission system-1996 and later models shown



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Fig. Fig. 3: Common emission hose routing label-1996-99 4.3L models



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Fig. Fig. 4: Typical emission hose routing label-1996-99 2.2L models

This system is designed to limit gasoline vapor, which normally escapes from the fuel tank and the intake manifold, from discharging into the atmosphere. Vapor absorption is accomplished through the use of the charcoal canister. The canister absorbs fuel vapors and stores them until they can be removed and burned in the combustion process. Removal of the vapors from the canister to the engine is accomplished through a computer controlled canister purge solenoid.

In addition to the canister, the fuel tank requires a non-vented gas cap. This cap does not allow fuel vapor to discharge into the atmosphere. All fuel vapor travels through a vent line (inserted high into the domed fuel tank) directly to the canister.

SERVICING



Every 30,000 miles (48,000 km) or 24 months, check all fuel, vapor lines and hoses for proper hook-up, routing and condition. If equipped, check that the bowl vent and purge valves work properly. Remove the canister and check for cracks or damage and replace, if necessary.

 
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