Westerbeke W-46 - Page 70

FUEL SYSTEM
When tested on the nozzle tester, the injection nozzle can reproduce
these two spray types for visual inspection. Initial throttled spray
occurs when the tester lever is operated at a rate of 60 cycles-per-
minute (up and down in one second); terminating main spray occurs
when the lever is operated rapidly at a rate of 4 to 6
cycles-per-second.
a. Initial Throttle Spray
When the nozzle is producing this spray only, the atomization is
generally poor and the pattern is straight then conical. Evidence
of after-dribble, fuel dribbling after injection, is also present.
All these are due to the injected fuel being throttled by the
pintle protruding from the valve.
While the nozzle is producing this spray, check the needle valve
for chattering in synchronism with the cyclic motion of the lever;
if so, then the needle valve is free from any sticking or hitching
tendency. If not, the nozzle and needle valve must be cleaned by
washing and then re-tested.
Evidence of off-center spray or directionally-erratic spray, indi-
cates that the injection nozzle needs thorough cleaning.
b. Terminating Main Spray
With the tester lever operated at a rate of 4 to 6 cycles-per-
second, the initial throttle spray is minimally visible. The
spray under this condition may be regarded as main spray.
The main spray should be a good straight cone, consisting of
finely-atomized fuel particles without any large droplets, finely-
atomized fuel particles without any large droplets, and should
terminate with no dribble or dripping fuel at the tip.
Seating Tightness
An injection nozzle, tested and adjusted as above, and found to pro-
duce a good spray pattern, may be re-used in the engine, provided that
it passes this final test: seating tightness test.'
With the injection nozzle mounted on the nozzle tester, raise the
pressure slowly to 100 or 110kg/cm2 (1422 or 1564psi), without
exceeding the set pressure of 120kg/cm2 (1706psi), so that the needle
valve will not unseat. Hold the pressure and observe the nozzle tip;
there should be no evidence of fuel oozing out to form a dribble. If
such evidence is noted, the contactlng faces of the needle valve and
seat must be repaired by lapping in the manner previously suggested or
the entire injection nozzle must be replaced.
(NOTE: Check injection nozzle for spray pattern every 1200
hours and remove carbon deposits around nozzle tip. Over-
haul or replace as needed.)
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