Onan DJA Series User Manual

WORK TRANSFER
PRIMING LEVER
FUTER.
REMOVE BLEED PIUG FROM
TOP OF FUEL FILTER.
ALLOW FUEL TO FLOW
FROM BLEEDER HOLE
UNTIL NO AIR BUBBLES
APPEAR;
FIG. 6-2
Next run the engine at governed speed on fuel provided by
gravity feed and measure the fuel pump pressure developed.
Pressure should be between 3-1/4 and 4-1/2 psi with the
gauge 16" above the fuel pump.
A low pressure reading indicates extreme wear in one part
or some wear in all parts, and the pump should be overhauled
or replaced. If the reading is above maximum, the diaphragm
is probably too tight or the diaphragm spring too strong. This
can also be caused by fuel seeping under the diaphragm
retainer nut and between the diaphragm layers, causing a
bulge in the diaphragm. Overhaul the pump and replace the
defective parts.
Low pressure with little or no pressure leak after pumping
stops indicates a weak or broken spring or worn linkage and
in most cases the pump should be replaced.
Fuel Pump Removal Disassembly:
1. Remove the pump inlet and outlet lines. Remove the
two cap screws holding the pump to the engine and lift
it off.
2. Notch the pump cover and body with a file so they can
be assembled inthe same relative positions,and remove
Ae six screws holding them together.
3. Tap the body with a screwdriver to separate the two
parts. Do not pry them apart - this would damage the
diaphragm.
4. Lift out the diaphragm assembly and diaphragm spring.
Repair: Transfer pump failure, is usually due to a leaking
diaphragm, valve or valve gasket. A kit is available for
replacement of these parts. Because the extent of wear
cannot be detected by the eye, replace all parts in the kit.
If the diaphragm is broken or leaks, check for diluted
crankcase oil and replace.
Occasionally, failure is due to a broken or weak spring or
wear in the linkage. In this case, replace the worn parts
or install a new pump. Obtain replacement parts other than
the repair kit from an original equipment parts distributor.
Assembly:
1. When installing a new diaphragm, soak it in fuel before
assembling. Insert the diaphragm spring and soaked
diaphragm into the pump body.
2. Compress the rocker spring and install between the
body and rocker arm.
3. Assemble the cover to the body with notch marks lined
up. Install the screws but do not tighten.
4. Push the rocker arm in full stroke and hold in this
position to flex the diaphragm. Important: The
diaphragm must be flexed or it will deliver too much
fuel pressure.
5. Tighten the cover screws alternately and securely, then,
release the rocker arm.
6. Install the pump on the engine and repeat the pressure
test.
NOZZLE
The American Bosch injection nozzle is the conventional
inward opening pintle type with adjustable opening pressure.
It is factory adjusted to open at 1,900-to 1,950-psi. After
several hundred hours of operation the nozzle pressure will
decrease to approximately 1750-psi. Do not disassemble
the nozzle or adjust nozzle pressure without proper test
equipment. A nozzle pressure tester is essential to do this
work.
FUEL PUMP
OUTLET
FIG. 6-3
13

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English