Fuel Selector Valves: Operation

Two types of valves are used on General Motors trucks. Those models with a fuel return system use a 6-port valve, while those without a fuel return system use a 3-port valve.

Valve operation is the same for both valves. When the instrument panel switch is in the Auxiliary (left-hand) position, selector valve solenoid is energized. When switch is in Main (right-hand) position, selector valve solenoid is de-energized.

The dash switch is energized only when the ignition is "ON". When vehicle is operated in the Auxiliary switch position, fuel in the feed lines as well as return lines (if equipped) will always return to the main tank when ignition is turned off. Operation in the Auxiliary switch position with main tank full will result in overfilling of main tank.