Onan DJA Series User Manual

WORK TRANSFER PUMP
PRIMING LEVER TO FILL
FILTER
NOTE: IF PRIMING LEVER
DOES NOT ENGAGE CRANK
ENGINE ONE REVOLUTION
REMOVE BLEED PLUG FROM
TOP OF FUEL FILTER
ALLOW FUEL TO FLOW
FROM BLEEDER HOLE
UNTIL NO AIR BUBBLES
APPEAR.
FIGURE 12. BLEEDING FUEL SYSTEM (PRIOR
TO SPEC S)
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 inches above the fuel pump.
Repair: Transfer pump failure is usually due to a leak-
ing 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
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.
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 maxi-
mum, the diaphragm is probably too tight or the dia-
phragm 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. See Figure 14.
NOZZLE
The American Bosch injection nozzle is the convention-
al inward opening pintle type with adjustable opening
pressure. It is factory adjusted to open at 1900 to 1950
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.
Low pressure with little or no pressure leak after pump-
ing 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 in the same relative positions,
and remove the 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.
FUEL PUMP
OUTLET
FIGURE 13. FUEL PRESSURE GAUGE
17

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English