An internal vent drilling (1) in the pressure regulator cavity
allows any oil that has leaked past the plunger into the
spring cavity to drain back into the oil pan.
The regulator plunger remains in the downward or open
position until the main oil rifle pressure drops below 275
kPa [40 psi].
At that time, the regulator spring force is high enough to
overcome the oil pressure signal from the main rifle. The
regulator plunger moves upward or closed once again,
blocking off the dump port to the oil pan.
STC Engines are equipped with a viscosity sensor which
is in series with the main oil rifle pressure signal line and
the lubricating oil pump pressure regulator. The purpose
of the viscosity sensor is to increase lubricating system
pressures to the STC injector tappets when the oil is cold.
The viscosity sensor changes the oil pressure as a func-
tion of oil temperature. It raises oil pressure when the oil
is cold (more viscous), and lowers the oil pressure to
normal operating pressure when the oil is warm (less
viscous).
Oil Temperature Oil Pressure at the Main Oil Rifle
°C [°F] Low Idle
kPa [psi]
High Idle
kPa [psi]
0 [32] 450 to 690 [65 to 100] 490 to 770 [70 to 110]
21 [70] 350 to 590 [50 to 85] 380 to 660 [55 to 95]
93 [200] 100 [15] 240 to 310 [35 to 45]
Lubricating System General Information Section 2 - Lubricating System
N14Page 2-4
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