Westerbeke W-46 - Page 69

FUEL SYSTEM ,
3. Testing and Adjustment
Injection Pressure
The pressure at which the needle valve unseats itself against
the force -of the pressure spring is referred to as valve
o~ning pl'.'essure or beginning-of-injection· pressure,
however, it will be referred to as .injection .EE,essure in this
manual. The value of this pressure is specified; it is checked
and adjusted as follows:
a. Install the injection nozzle in the nozzle tester, and
operate the manual· pumping handle of the tester several
times to prime the nozzle.
b. Move the lever in an up-and-down cycle of one per second to
pressurize the injection nozzle, while observing the indica-
tion of the test pressure gauge. As the nozzle begins to
spray, the deflected gauge needle will indicate the
injection pressure.
Specifications
Unit: kg/cm
2
(psi)
Item
Standard
Repair
limit
Injection
12o+
1
g (1706.4+
14
5·
2
)
ll 0 (1564.2)
pressure
max
c. If the indicator reading is below the limit, increase the
thickness of the washer used on the pressure spring.
Increasing the washer thickness by lmm (0.04in.) increases
the injection pressure by about l0kg/cm2 (l42psi). Washer
stock for adjustment purposes is available in 20 sizes,
ranging from l.Omm (0.0394in.) up to l.95mm (0.0768in.),
in increments of o.osmm (0.0020in.) each.
Spray Pat tern
The injection nozzles used in the present engine are the
thrqttle type. Some throttling action tak.es place when the
needle valve begins to unseat, limiting the amount of sprayed
. fuel during the initial stage of each fuel i~jection. Thus,
each slug of sprayed fuel may be regarded as comprised of two
portions; initial throttled spray and terminating main spray.
Checking injection pressure
on nozzJ.e tester
1 2 3 4 5 6
1111 Ill llUJ ' /i\ '}f'
/ i! \, Jjl·\)
~
1-Good 4-After-dr ibble
2-Spray cone too large 5-fissured spray
3-0ff center spray 6-\-Jhirling spray
Possible patterns of spray
67