Onan DJA Series User Manual

FUEL SYSTEM
The diesel fuel system provides a means of filtering, trans-
porting and delivering fuel in a fine spray to the engine
cylinder at the correct time for ignition. The system con-
sists of a primary fuel filter, fuel transfer pump, secondary
fuel filter, injection pump and an injection nozzle.
The diaphragjn fuel transfer pump which operates directly
off the engine camshaft, draws fuel from a supply tank and
delivers it through two filters to the injection pump. The
injection pump meters fuel and delivers it, at high pres-
sure to the injection nozzle at the correct time for ignition.
The injection nozzle opens at a set fuel pressure, delivering
fuel in a fine spray, to the precombustion chamber for igni-
tion. The nozzle remains open, delivering fuel as long as
the fuel pressure remains above the critical point.
Caution: Dirt in the iuel system is a diesel engines worst
enemy. It is one ol the major causes ol diesel engine
failure. Even a tiny piece ol dirt in the injection system
may stop your unit. When opening any part ol the fuel
system beyond the secondary fuel filter, place all parts in
a pan of clean diesel fuel as they are removed. Beiore
installing new or used parts, Hush them thoroughly and
install while still wet.
MAINTENANCE
In addition to regular service periods, change the secondary
fuel filter cartridge if the engine shows signs of starving
from lack of fuel. Remove the secondary filter by removing
the large cap screw in the center of the filter cover. Use
care when replacing the filter cartridge to avoid getting
dirt into the injection pump passages.
Extra fuel is bled off after each injection cycle by a fuel
retum line from the nozzle. An adapter combines the leak-
off fuel with the flow-through fuel from the injection pump.
A return line connected at this point, returns the combined
fuel back to the fuel supply tank.
AIR
CLEANER
MANIFOLD
HEATER
6LOW PLUS-
CRANKCASE
BREATHER TUBE
FUEL FILTER
SEDIMENT
BOWL
PRIMARY
FUEL FILTER
INJECTION
NOZZLE
FUEL
RETURN LINE
INJECTION
PUMP
SECONDARY
FUEL FILTER
Beginning With Spec T
FIG. 6-1
When replacing or cleaning filters, bleed the fuel system.
Do this by opening the air bleed screw located on top of the
secondary filter removal cap screw. Operate the hand prim-
ing lever on the transfer pump until no air bubbles flow from
the bleed screw hole, then tighten the bleed screw. Return
the priming lever to its original position (Fig. 6-2).
Important: If the transfer pump cam lobe is on the high side
the priming lever will not operate the pump. Turn the engine
one revolution before operating the priming lever.
FUEL TRANSFER PUMP
The transfer pump is located on the left side of the engine.
If fuel does not reach the secondary filter, make the follow-
ing checks before removing the pump.
1. Check the fuel tank and see that the shut-off valve is
open.
2. Remove the fuel line from the transfer pump outlet and
work the priming lever on the pump. Fuel should spurt
out of the pump. If not, remove the pump for repair or
replacement.
Testing: If the transfer pump delivers fuel, test it with a
pressure gage or manometer. Perform these tests before
removing the pump from the engine. Remove the pump outlet
and install the pressure gage (Fig. 6-3) .
Test the valves and diaphragm by operating the primer lever
a few times and watching the pressure. It should not drop
off rapidly after priming has stopped.
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Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English