Opel 1900 1973 Service Manual page 410

Figure 7C-26
the sump. The oil is carried past the crescent section
of the pump, beyond which the gear teeth begin to
come together, pressurizing the oil as it is
from between the gear teeth. The pressurizeh oil is
then delivered through the pump outlet to the hy-
draulic control system.
If the vehicle has not been operated for a while, the
oil in the pump cavity tends to drain and leak back
to the sump. With the pump cavity filled with air, the
pump cannot develop enough suction to lift the oil
from the sump. For this reason, a priming valve is
located in the pump pressure passage. As the air in
the pump is compressed by the gears, it is forced out
through the bleed orifice in the priming valve and
into the exhausted cavity behind the reverse piston.
This permits the pump to prime and draw oil from
the sump. As soon as the hydraulic pressure reaches
15 PSI: the valve is forced over closing off the bleed
orifice.
In the hydraulic control circuit, there are four major
types of iontrol elements. These categories along
with the specific items are listed below.
A.
Pressure regulating valves.
Governor Assembly And Speedometer Drive Gear
1. Main pressure regulator valve.
squeezed
2. Modulator valve.
AUTOMATIC TRANSMISSION
PRIMING VALVE PRIMING VALVE