Courtesy of GENERAL MOTORS CORP.
When operating in V8 mode, the active fuel management valve lifters function similar to the non-
active fuel management valve lifters. The active fuel management oil manifold solenoids are in
the closed position, with no pressurized oil directed to the valve lifters. The pushrod (1) travels
upward and downward to actuate the rocker arm and valve. The spring loaded locking pins (5) of
the lifter are extended outward and mechanically lock the pin housing (4) to the outer body of the
valve lifter (3).
When the active fuel management system is commanded ON, the ECM will direct the solenoids
of the oil manifold to open and direct pressurized oil to the valve lifters. Oil travels through the
valve lifter oil manifold and engine block oil galleries and enters the inlet port (6) of the valve
lifter.
When operating in V4 mode, pressurized oil forces the locking pins (11) inward. The pushrod (7)
remains in a constant position and does not travel upward and downward. The outer body of the
lifter (9) moves upward and downward independently from the pin housing (10). The valve lifter
spring (8) retains tension on the valve train components to eliminate valve train noise.
When the active fuel management system is commanded OFF, the ECM directs the solenoids of
the oil manifold to close, stopping the flow of pressurized oil to the valve lifters. The oil pressure
within the lifter will decrease and the locking pins will move outward to mechanically lock the
pin housing and outer body.
Engine Block
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,
Sierra & Silverado