OIL
SYSTEM
Onan diesel engines have pressure lubrication to all
working parts of the engine. The oil system includes
an oil intake cup, a gear-type oil pump, a by-pass
valve, a full-flow oil filter and passages and drillings
through the block for oil delivery.
Figure
38
shows the pressure oil system.
A
thin film of oil from the crankcase lubricates the
cylinder walls and the rings wipe the excess oil off to
prevent passage of oil to the combustion chamber.
The upper portion of the cylinders are partially
lubricated by the fuel. The connecting rod bearings
are critically in need of lubrication because of the
high pressures and high rotating speeds. Bearing
lubrication and cooling are very important to the life
of an engine.
Normal oil pressure should be
25
psi
(172.5
kPa) or
higher when the engine is at operating temperature.
If
pressure drops below
20
psi (138 kPa) at governed
speed, inspect the oil system for faulty components.
OIL
PUMP
The oil pump is mounted on the front
of
the crankcase
behind the gear cover and is driven by the crankshaft
gear.
The pump drawsoil from thecrankcase anddeliversit
through the oil filter to the rocker housing, drillings
through the crankcase to the crankshaft bearings,
camshaft front bearing, crankshaft passages to con-
necting rod bearings and connecting rod passages to
piston pin bushings.
Removal
1.
Remove gear cover and
oil
base. (See
ENGINE
2.
Unscrew intake cup from pump.
3.
Remove crankshaft lock ring and gear-retaining
4.
Loosen two cap screws holding pump and
DISASSEMBLY.
washer.
remove pump.
FIGURE
38.
OIL
PRESSURE
SYSTEM
Repair
Except for the gaskets, component parts of the pump
are not individually available.
If
the pump is defective
or excessively worn, replace it. Disassemble the
pump by removing the two cap screws holding the
pump cover to the body. Inspect forexcessive wear in
gears and shafts. To improve pump performance,
adjust the gear end clearance by changing the gasket
thickness between the pump body and cover. Usethe
thinnest gasket that permits free movement of the
pumpshafts. Oil all parts when assembling the pump.
Installation
Before installing,
fill
the pump intake and outlet with
oil to be sure
it
is primed. Mount the pump on the
engine and adjust the 0.005-inch
(0.127
mm) lash
between the pump gear and crankshaft gear. Mount
the intake cup on the pump
so
it is parallel to the
bottom of the crankcase.
30
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