DV11
Operation and Maintenance
124
Common Rail Fuel-injection System
Printed in Mar. 2005 PS-MMA0608-E1A
3.4.12. Pressure limiter valve
z The pressure limiter valve is at the connection end to the common rail, is closed
by the cone shaped end of the plunger valve against inside of the valve body. At
normal operating pressures (1600bar), a spring forces the plunger against the
seat and the common rail remains closed.
z As soon as the operating pressure is exceeded, the plunger is forced by the rail
pressure against the force of the spring, the fuel pressure is maintained with the
normal pressure, and the escape fuel return to the fuel tank through the return
pipe.
3.4.13. Injector
z The start of injection and the injected fuel quantity are adjusted by the solenoid
valve of the injector. These injectors supersede the nozzle and nozzle holder of
the existing engine. The fuel is fed from the high pressure connector, to the
nozzle through the passage, and to the control chamber through the feed orifice.
z The control chamber is connected to the fuel return via a bleed orifice which is
opened by the solenoid valve. With the bleed orifice closed, the hydraulic force
applied to the valve control plunger exceeds that at the nozzle needle pressure
shoulder. As a result, the needle is forced into its seat and seals off the high
pressure passage from the combustion chamber.
z When the injector's solenoid valve is triggered, the bleed orifice is opened. This
leads to a drop in control-chamber pressure and, as a result, the hydraulic
pressure on the plunger also drops. As soon as the hydraulic force drops below
the force on the nozzle-needle pressure shoulder, the nozzle needle opens and
fuel is injected through the spray holes into the combustion chamber.
Valve
Plunger
Valve spring
Valve body
Common
rail
Fuel
return
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