YANGDONG SERIES Y85 Operation & Maintenance Manual page 26

successively,and observe the exhaust smoke. When the cylinder with the faulty injector stops
firing,black smoke would disappear and engine speed is not appreciably affected or not affected
at alLlt may also be checked by listening to the chattering action of the injector of ever;' cylinder
with the flywheel rotating.If the distinct clear shall) sound of certain cylinder could not be heard,
the injector in this cylinder may be faulty.
I.Procedure of injector testing and adjustment
(1 ) Work the injector tester hand pump until the gauge pressure reaches about specified
injection pressure. Then operate the hand pump slowly and adjust the injection
pre~sure
at which
unjection begins. The nozzle should not show any signs of leakage. If fuel drips around the nozzle
tip after several tests, the nozzle set must be dismantled for cleaning and grinding. Then test it
agam.
(2)Remove the lock nut.turn the adjusting screw to get the pressure at the be-ginning of
injection which should be specified value in section l.Then tighten the lock nut,and test it agam.
(3 )Work the hanJ pump at a rate of approximately 1 stroke per second and ob- erve the
nl)zzlp spray.The fud !>pray should be even,and \\ell atomizeJ in a ,>hape of cone.At any cross
section of the cone,the atomized fuel should be finely and evenly distributed.Fuel droplets and
irregular pattern which can be seen by naked eyes should not be pre!>ent in the spray.There
should be a distinct clear sharp sound at the end of injectioll.Generally,irregular pattern of the
spray is caused by needle valve seizure, fuel dripping is generated by damaged conical sealing
surface of needle valve
a~d
spray split results from carbon deposits on the tip of nozzle and its
heat deformation.
2 Injector dismantlement and repair
(1 )Beforp dismantlmg the injector.clean off the dirt gathered on it .Clamp the nozzle body
ill a pliers !In<·d bv copper sheets, on its jaw with the nozzlp upward.Turn off the nozzh cap nut
.
and take out the nozzle set.Draw out the needle valve from the nozzle Lody and oak it in clean
fuel oil.Then clamp the injector in the vice upside down again.Dismantle the aJjusting nut,and
adjusting screw.then take out the injpctor spring and spindle.
(2) If the nozzle set is seized or emits fuel badly, it must be cleaned.Soak the seized nozzle
in fuel oil [or a while,and clamp the needle valve by a pliers with cloth lined. Then rotate and
draw it out slowly,just to avoid scratching its surface. Decarbonize the needle valve and nozzle
body with woodern chip soaked in fuel oiLlt is forbidden to clean them with metal chip.If the
guiding surface of the needle valve and nozzle body is not smooth enough.it may be lapped with
4-3
t