RAM 3500 Chassis Cab Truck 2WD L6-6.7L DSL Turbo (2010)
Fuel Injector: Description and Operation
Operation
OPERATION
High-pressure fuel is supplied from the injection pump, through a high-pressure fuel line, into a fuel rail, through high-pressure lines, through steel
connectors and into the solenoid actuated fuel injector. The Powertrain Control Module (PCM) actuates the solenoid causing the needle valve to rise and
fuel flows through the spray holes in the nozzle tip into the combustion chamber.
Each fuel injector is connected to the fuel rail by a high-pressure fuel line and a steel connector. This steel connector is positioned into the cylinder head
and sealed with an O-ring. The connector is retained in the cylinder head by a nut (fitting) that is threaded into the cylinder head.
The torquing force of this threaded nut (fitting) provides a sealing pressure between the fuel line connector and the fuel injector. Retaining nut torque is
very critical. If the nut (fitting) is under torqued, the mating surfaces will not seal and a high-pressure fuel leak will result. If the fitting is over torqued,
the connector and injector will deform and also cause a high-pressure fuel leak. This leak will be inside the cylinder head and will not be visible. The
result will be a possible fuel injector miss-fire and low power, or a no-start condition.
The fuel injectors use hole type nozzles. High-pressure flows into the side of the injector, the PCM activates the solenoid causing the injector needle to
lift and fuel to be injected. The clearances in the nozzle bore are extremely small and any dirt or contaminants will cause the injector to stick. Because of
this, it is very important to do a thorough cleaning of any lines before opening up any fuel system component. Always cover or cap any open fuel
connections before a fuel system repair is performed.
Each fuel injector connector tube contains an edge filter that is designed to break up small contaminants before entering the fuel injector. The edge
filters are not a substitute for proper cleaning and covering of all fuel system components during repair.
The bottom of each fuel injector is sealed to the cylinder head with a 1.5 mm thick copper shim (gasket). The correct thickness shim must always be
re-installed after removing an injector.
Fuel pressure in the injector circuit decreases after injection. The injector needle valve is immediately closed and fuel flow into the combustion chamber
is stopped. Exhaust gases are prevented from entering the injector nozzle by the needle valve.
