Service Manual
PRESSURE
LUBRICATION
All
engines use an oil pump to provide a constant flow of
oil to the engine parts. The oil supply collects in the oil
base where it is picked up by the oil pump pick-up cup.
A
by-pass valve is used to control oil pressure. Drain oil
before removing oil base and always use a new gasket
when replacing the oil base.
Oil
Pump
The
oil
pump (Figure 4) is mounted behind the gear
cover and is driven by the crankshaft gear. Inlet pipe and
screen assembly are attached directly to the pump
body.
A
discharge passage in pump cover registers with
a drilled passage in the crankcase. Parallel passages
distribute oil to the front and rear main bearing and the
oil bypass valve.
OIL PUMP PICK-UP CUP
OIL
PUMP ASSEMBLY
CRANKCASE TURNED
ON
LEFT SIDE
FIGURE
4.
OIL
PUMP
ASSEMBLY
Check oil pump thoroughly for worn
parts.
Oil pump to
prime it before reinstalling. Except for gaskets and pick-
up cup, component parts of the pump are not available
individually. Install a new pump assembly
if
any parts,
are worn,.
Oil
By-Pass
Valve
The by-pass valve (located to the right and behind gear
cover) controls oil pressure by allowing excess oil to
flow directly back to
the
crankcase. The valve limits oil
pressure to
a
maximum of about 20 psi (1
38
kPa) on the
P216, P218, and P220, and about
30
psi (207 kPa) on
the P224 at normal operating temperature.
The valve is non-adjustable and normally does not need
maintenance. Determine if valve is operating correctly
by inspecting plunger action as follows:
1.
Remove the cap screw located behind gear cover
and under governor arm.
2. Remove spring and plunger with a magnetic tool.
3.
Determine proper valve operation by checking the
spring and plunger according to the following
measurements:
Plunger Diameter
..........
0.3105 to 0.3125 in.
(7.89 to 7.94 mm)
Spring
Free Length
..............
1.00 inch
(25.4
mm)
Load
.....
.;.
....
.2.6
±
0.2 Ibs (11.6
±
0.9
N)
when compressed to
0.5
inch (12.7 mm)
4.
5.
Check the valve seat and clean away any accumu-
lation, of metal particles which could cause erratic
valve, action. Verify that the valve seat is not
damaged.
Clean plunger and spring in parts cleaning solvent
and install.
Circumferential grooves in the main bearings supply oil
to connecting rod bearings through drilled passages
from each main journal.
A
drilled passage connects the
front main bearing oil supply to the front camshaft
bearing; rear cam bearing is splash lubricated.
Normal oil pressure should be
8
psi
(55
kPa) or higher at
1500 rpm when the engine is at normal operating
temperature.
If
pressure at 1500 rpm drops below this
value, inspect oil system for faulty components.