Each cylinder has an identical fuel injection nozzle mounted in the pre-combustion chamber. The nozzles are secured with threads and copper sealing gaskets to ensure long-term seating and durability under high-pressure operation.
Each nozzle consists of a two-piece body. The upper body element includes the high-pressure inlet and a pair of leak-off ports. The lower body element consists of the nozzle nut. Each nozzle body houses the following components (figure 4-7):
โข a selective-thickness shim
โข an intermediate plate
โข a pressure spring
โข a pintle nozzle
โข a pressure spindle
โข a heat shield
As the pressure wave of injection reaches a nozzle, the needle valve is lifted against spring force and fuel exits into the pre-combustion chamber of the cylinder as a highly atomized spray. A small amount of fuel also travels between the needle valve and pintle nozzle to provide lubrication.
Two passages inside the upper half of the nozzle body allow fuel that has lubricated the needle valve to exit into the fuel return system. Fittings on the nozzle connect with hoses and clamps to the return system pipes.
During service, nozzles are serviced by replacement. Installation involves the use of a new compression gasket, anti-seize compound (GM P/N 1052771) on the cylinder head threads and a tightening torque of 60 to 80 N*m (44 to 59 Ib-ft), using a special socket.
