Mitsubishi 4DQ50 Service Manual page 73

Probable cause
Possible remedy
Excessive injection quantity
Stop lever jammed in "increase"
Repair lever link properly, placing
position.
lever in neutral position.
Improper full -load setting of
Adjust governor setting on bench.
governor
Loose plunger pinions
Reinstall properly by matching
stamped marks.
Improper fuel spray from Sticking needle valve (s) in one
Repair and replace nozzles if
injection nozzles or more nozzles necessary.
Damaged nozzle tip seats
Repair and replace seats if necessary.
Worn or broken nozzle springs
Replace nozzle springs.
Extremely low injection pressure
Adjust Pressure to 120 ± Skg/cm
2
(l706.4±71.l Ib/in
2 )
on nozzle
tester by inserting shim (s).
Carbon deposited on packings
Remove carbon.
at nozzle tips
Injection timing too advanced Improper installation of fuel
Re - time properly by tilting injection
Injection pump
pump toward engine.
Incorrect installation of timing
Re - time timing gear train.
gears
Injection timing to retarded Improper installation of fuel
Re - time properly by tilting injection
injection pump pump outward.
Incorrect meshing of timing Re - time timing gear train.
gears
Worn cams, tappets or bearings
Replace.
of fuel injection pump
Poor grade of fuel oil Poor grade of fuel oil Use good quality fuel.
Water in fuel Use good quality fuel.
Low oil pressure
Lack of oil in oil pan Add oil to prescribed level.
Air
in oil strainer Replace damaged pipes or packings.
Retighten loose parts.
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