Xinchai 490B Series Manual page 33

4.12 Adjustment of Injection Timing
In order to get the lowest fuel consumption rate and good performance, it's necessary
to adjust the injection timing.
The method of adjusting injection timing is as follows:
1尧 Release the air trapped in the fuel system. Repeatedly turn the crankshaft to and
fro to fill up the injection pump with fuel. Dismantle No.1 high pressure pipe. Blow away
the fuel in the delivery valve adapter. Slowly turn round the crankshaft clockwise and
watch the fuel in the adaptor. Stop the crankshaft as soon as the first sign of the fuel
moving up is discovered.
2尧 Check if the mark at the observing window on the flywheel housing or the
indicating pin on the gear housing cover points to the right timing marks on the flywheel
and V belt pulley respectively.
3尧 If the injection advancing angle is not right, loose three M8 nuts that fix the
injection pump on the gear housing. Turn the injection pump off the cylinder block if the
angle is too big or otherwise if too small.
4.13 Adjustment of Injector
The test and adjustment of injector should be done on the test stand. The purpose is
to adjust the injector pressure and watch the atomization quality and deal with the
troubles.
The steps for the adjustment of injector:
1冤Push the handle of the hand pump to raise the fuel pressure to 18MPa; Gradually
push the handle to further raise to 20.3 to 20.8MPa; watch the nozzle tip to see if there is
any fuel leakage or dripping. Check, wash, or lap the nozzle precision couple if necessary.
2冤Take down injector screw cap, tighten or loosen adjusting screw to get the injector
pressure to 20.3原20.8Mpa. Fix the screw cap and check again.
3冤Watch the atomization quality. Do the atomization test at a speed of every 1 second
each. The fuel atomization should be fine and even. No splashed fuel should be seen and
uneven or deflected spray is not allowed. Clear cut sound should be heard when the
injection stops. Generally, abnormal injection is caused by sluggish movement of the nozzle
needle valve, fuel dripping is caused by damaging of sealing surfaces, branching of spray is
caused by carbon deposit at nozzle tip or thermal deformation.
4.14 Adjustment of Injection Pump
Injection pump has been checked and adjusted before being released off the line. If
there is need to re-adjust, it should be done on a special testing machine by a professional
mechanic.
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