Onan DJA Series User Manual

OIL SYSTEM
DJA engines have pressure lubrication to all working
parts. The oil system includes oil intake cup, gear type
oil pump, bypass valve, oil pressure gauge, full-flow
oil filter, and block passages and drillings to deliver
oil throughout the engine (Figure 26). Oil is held in the
base, drawn by the pump, and delivered through the oil
filter. Lines leading to the rocker housing, drillings
through the block to crankshaft bearings and to front
camshaft bearing crankshaft passages to connecting
rod bearings and connection rod passages to piston pin
bushings complete the oil system plumbing.
The crankcase breather is included in this system
because it aids oil consumption control.
Oil pressure should be 25 psi or higher when the engine
is at normal operating temperature. If pressure drops
below 20psi at governed speed, inspect the oil system
for faulty components.
MAINTENANCE
Periodic oil system maintenance should include chang-
ing crankcase oil, cleaning the crankcase breather,
CRANKCASE
BREATHER
BYPASS
VALVE
OIL
PUMP
FIGURE 26. PRESSURE OIL SYSTEM
cleaning rocker box oil lines, and replacing the oil
filter. Consult the periodic service chart for service
periods.
OIL PUMP
The oil pump is mounted on the front of the crankcase
behind the gear cover and is driven by the crankshaft
gear.
Removal:
1. Remove the gear cover and oil base. (See Engine
Disassembly Section).
2. Unscrew the intake cup from the pump.
3. Remove the crankshaft lock ring and gear retaining
washer.
4. Loosen the two cap screws holding the pump and
remove pump.
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 for excessive wear in
gears and shafts. To improve pump performance, adjust
the gear end clearance by changing the gasket thick-
ness between the pump body and cover. Use the thin-
nest gasket that permits free movement of the pump
shaft. 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 for 0.005-inch lash between
the pump gear and crankshaft gear. Mount the intake cup
on the punp so it is parallel to the bottom of the
crankcase.
BYPASS VALVE
Located on the outside of the rear bearing plate, the
bypass valve (Figure 27) controls oil pressure by
allowing excess oil to flow directly back to the crank-
case. Normally the valve begins to open about 25 psi.
It is nonadjustable and normally requires no main-
tenance.
To determine if high oil pressure is caused by the
plunger sticking closed or low oil pressure by the
plunger sticking open, clean and inspect the valve.
To remove the valve, unscrew the recessed plug in the
rear bearing plate and lift out the spring and plunger
assembly. Determine proper valve operation by checking
the spring and plunger against the values following:
26

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English