Mitsubishi 4DQ50 Service Manual page 38

engine tries to run at a higher speed than A (r.p.m.), a consequential rise of
negative pressure provides greater governing force, which compresses main
spring against its setting load, thereby pulling back injection pump control rack
to reduce injection, and as the result, engine speed is slowed down to A
(r.p.m.). When, on the other hand, engine speed is made to fall below A
(r.p.m.), a decrease of negative pressure lets main spring press control rack
ahead to rise injection rate, whereby it is vised back to A (r.p.m.). Meanwhile,
the more Venturi butterfly valve throttles, the quicker rise of negative pressure
to engine speed can make engine keep low constant speed, by producing
governing force Fc. Governing the engine speed thus in one-to-one proportion
to the percentage of Venturi opening, this governor is called an all-speed type.
In case heavy load on the engine makes it run at a lower speed than equivent to
the Venturi opening (for example, lower than A even at 100% of Venturi
opening, in the diagram), control rack is pressed over its whole travel to full
load stopper, making it to develop max. torque. If "tough" torque is required
of the engine, governor is equipped with a buitin torque spring (angleich
spring).
3) This type of governor requires espeCially perfect air-tightness of air pipe and
intake system, for lack of their air-tightness will much affect its performance
and cause particularly overrunning.
Into air chamber for atmospheric pressure in diaphragm block negative pressure
is lead from inside paper element of air cleaner through vinyl tube so as to
compensate the change of resistance the might arise from its clogging.
4) Being of sheep skin, diaphragm in diaphragm block requires regular lubrication.
(Refer to "Lubrication".) When a sudden unusual change noticed in idling,
have it checked by your dealer or at a service shop, as it is suspected to be
broken from aging.
Each time to apply oil to diaphragm, loosen red plug ~n the side of diaphragm
block to draw off the excess of diaphragm oil or fuel collected there from
pump. If too much fuel found there, make necessary repairs.
5) In any case whatever, don't tamper with the seals on (Fig. 3-26, 3-27)
I njection pump full load stopper Seal
Diaphragm block cover Seal 2
'Idling sub-spring Seal 3
Venturi lever stopper ("full-open" side) Seal 4
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