right out of the onan manual
Onan 4000 manualChoke Assembly
The genset has an automatic choke assembly that
consists of a bimetal choke coil, coil housing, heater
tube (from the exhaust tube), and choke linkage.
The choke linkage connects to the choke shaft lever
on the carburetor.
When the engine is cold, the choke coil position
causes the linkage to hold the choke nearly closed.
When the engine starts, hot air from the exhaust
manifold enters the coil housing. The choke coil expands
pulling the linkage to partially open the
choke. As the engine warms up, the coil continues
to expand and gradually opens the choke and holds
it open while the engine is operating. This action
varies the fuel/air mixture as the engine warms up to
provide smooth engine operation.
If the engine starts but runs rough and exhausts
black smoke after a minute or two of operation, the
choke setting is too rich. If the engine starts but
sputters or stops before it warms up, the choke setting
is too lean.
Choke Adjustment: Check the choke linkage to
make sure it is not bent or rubbing. Rotate the choke
lever on the carburetor. The choke shaft should
move freely and it should return to its original position
when released. Inspect the heater hose to
make sure it is installed properly and in good condition.
Refer to Figure 8-15 on Page 8-18.
WARNING The choke housing becomes very
hot during operation and can cause severe
burns if touched. Allow the genset to cool down
before handling the choke assembly.
1. Allow the genset to cool down. The temperature
inside the housing must be the same as
the ambient temperature.
2. Loosen the adjustment screw holding the adjustment
plate.
3. Slowly rotate the adjustment plate until the bimetal
choke shaft connection is visible in the
sight window. This is the correct setting for an
ambient temperature of 70° F (21° C).
If the ambient temperature is higher or lower
than 70° F (21° C), make a mark on the choke
coil housing opposite the center mark on the
adjustment plate. Each mark on the adjustment
plate is equal to 10° F (12.2° C) of difference
from 70°F (21°C). If it is warmer than 70°F (21°
C), rotate the plate clockwise. If the temperature
is less than 70° F (21° C), rotate the plate
counterclockwise. Tighten the adjustment
screw.
Example: If the ambient temperature is 90° F
(32° C), rotate the adjustment plate two marks
clockwise from the 70° F (21° C) position
marked on the housing.
4. Move the choke lever back and forth to check
for free movement. Verify that the choke does
not bind or stick.
