B3.9 and B5.9 Series Engines
Section 6 - Injectors and Fuel Lines - Group 06
High-Pressure Fuel Lines
The pressure of the fuel in the line is sufficient to pen-
etrate the skin and cause serious bodily harm.
Check for air in the high-pressure lines by loosening the
fittings at the cylinder head, and crank the engine to allow
entrapped air to bleed from the line. Tighten the fittings.
Do not bleed a hot engine as this can cause fuel to spill
onto a hot exhaust manifold, creating a danger of fire.
Operate the engine, and vent one line at a time until the
engine runs smoothly.
Use only the specified injector for the engine.
All engines use closed nozzle, hole-type injectors. How-
ever, the injectors can have different part numbers for dif-
ferent engine ratings. The last four digits of the Cummins
part number are used to identify the injectors.
During the injection cycle, high pressure from the injection
pump rises to the operating (pop) pressure, which causes
the needle valve in the injector to lift. Fuel is then injected
into the cylinder. A shimmed spring is used to force the
needle valve closed as the injection pressure drops below
the pop pressure to seal off the nozzle after injection.