Onan DJA Series User Manual

REPAIR, STARTING MOTOR
Armature: Inspect the armature for mechanical defects
before checking for ground or shorted coils.
To test for grounds, use a 12-volt test lamp and check
between each segment of the commutator and the shaft.
Do not touch probes to the commutator brush surfaces;
this will burn the smooth surfaces.
A growler is necessary to test for shorted coils. With
the armature in the growler, run a steel strip over the
armature surfaces. If a coil is shorted, the steel strip
will become magnetized arid vibrate. Rotate the arma-
ture slightly and repeat the test. Do this for one
complete revolution of the armature. Replace the
armature if it has a short or ground.
If the commutator is only dirty or discolored, clean it
with No. 00 or 000 sandpaper. Blow the sand out of the
motor after cleaning. If however, it is scored, rough, or
worn, turn it down in a lathe.
Field Coils: Using a 120-volt test lamp and probes,
check the field coils for grounding to the motor frame
or open circuit. Inspect all connections to be sure they
are properly clinched and soldered. Inspect the insula-
tion for evidences of damage. The only way to check
for field coil shorts is to use the test at the beginning
of this section.
Bearings: If either the front or rear bearings show ex-
cessive wear, replace them. Drive the old bearings out,
and using an arbor press and the proper arbor, press
new bearings into place. The outer pinion bearing must
be flush with the bearing bore on the inside of the
bearing.
PUSH PLUNGER
STOP
STARTING MOTOR NEED
NOT BE REMOVED FROM
ENGINE TO MAKE THIS
MEASUREMENT
FEELER GAUGE
(0.07"-0.12" CLEARANCE.
SEE TEXT)
FIGURE 32. PINION CLEARANCE
Brushes: Check the brushes for wear or improper seat-
ing. They should slide freely in their holders. Check
the brush spring tension with a spring scale. To change
spring tension, twist the spring at the holder with long
nose pliers.
If brushes are excessively worn, replace them.
Some brushes are soldered to the field coil lead. Un-
solder thie lead and open the loop in the field coil
lead. Insert the new brush pigtail completely into the
loop and clinch before" resoldering. A good soldering
job is necessary to insure good contact and low voltage
drop across the connection.
Over-Running Clutch: Clean the clutch thoroughly
but do not dip in solvent. It cannot be repacked with
grease.
It should slide easily on the armature shaft with no
binding. Turn the pinion; it should rotate smoothly, but
not necessarily freely. Reverse the direction of a few
times and it should instantly lock and unlock. Replace
the clutch if operation is defective or pinion is worn or
damaged.
Shifting Solenoid: Check to be sure plunger moves
freely in coil. Measure the pull-in coil current draw
by connecting a battery, voltmeter and ammeter to the
control terminal and the terminal to the motor. Measure
the hold in coil draw from the control terminal to
ground. Inspect the switch for corrosion and clean the
contacts if necessary. Replace the solenoid if the
current draw is not within limits when cleaned.
ASSEMBLY, STARTING MOTOR
Before assembling, soak the bronze bearings in oil.
They are absorbent bearings, designed to hold up to
25 percent of their own weight in oil. Be sure the felt
oil pad is in the outer end of the commutator end bear-
ing.
When the. motor is assembled, check the armature end
play. It should be between 0.005-inch and 0.030-inch.
Adjust end play by adding or removing washers on the
armature.
Before installing, check the pinion clearance. Proper
clearance is important to insure starter engagement.
Press on solenoid core to shift the pinion into full
mesh and measure the clearance between pinion and
stop (Figure 32). This should be between 0.070-inch
and 0.120-inch (as near to 0.070-inch as possible).
Adjust the link screw on the end of the solenoid plung-
er for proper clearance.
IMPORTANT: On units built prior to serial No. 679677,
it was necessary to maintain the gap between ring gear
and starter pinion in the relaxed position at less than
1/8-inch to insure starter engagement. When installing
these motors, check this gap. If it is too great, a shim
kit is available to reduce it. See Figure 31.
30

Onan DJA Series Specifications

General

Brand	Onan
Model	DJA Series
Category	Engine
Language	English