Kohler COMMAND CH18, Service Manual

Page: 84 / 232

5B.15
Section 5B
EFI Fuel System
5B
When the key switch is on and the relay is closed, the
fuel rail is pressurized, and voltage is present at the
injector. At the proper instant, the ECU completes the
ground circuit, energizing the injector. The valve
needle in the injector is opened electromagnetically,
and the pressure in the fuel rail forces fuel down
through the inside. The “director plate” at the tip of
the injector (see inset) contains a series of calibrated
openings which directs the fuel into the manifold in a
cone-shaped spray pattern. Service
Injector problems typically fall into three general
categories: electrical, dirty/clogged, or leakage. An
electrical problem usually causes one or both of the
injectors to stop functioning. Several methods may be
used to check if the injectors are operating.
1. With the engine running at idle, feel for
operational vibration, indicating that they are
opening and closing.
2. When temperatures prohibit touching, listen for a
buzzing or clicking sound with a screwdriver or
mechanic’s stethoscope (see Figure 5B-19).
Figure 5B-18. Fuel Injector Details.
The injector is opened and closed once for each
crankshaft revolution, however, only one-half the
total amount of fuel needed for one firing is injected
during each opening. The amount of fuel injected is
controlled by the ECU and determined by the length
of time the valve needle is held open, also referred to
as the “injection duration” or “pulse width”. It may
vary in length from 1.5-8 milliseconds depending on
the speed and load requirements of the engine.
Figure 5B-19. Checking Injectors.
3. Disconnect the electrical connector from an
injector and listen for a change in idle
performance (only running on one cylinder) or a
change in injector noise or vibration.
If an injector is not operating, it can indicate either a
bad injector, or a wiring/electrical connection problem.
Check as follows:
NOTE: Do not apply voltage to the fuel injector(s).
Excessive voltage will burn out the
injector(s).
Do not ground the injector(s) with
the ignition “on” . Injector(s) will open/turn
on if relay is energized.
1. Disconnect the electrical connector from both
injectors. Plug the 12 volt Noid Light (part of EFI
Service Kit, see Section 2) in one connector.
1. Filter strainer in fuel supply
2. Electrical connection
3. Solenoid winding
4. Valve housing
Multi-Orifice
Director Plate with
Calibrated Opening
5. Armature
6. Valve body
7. Valve needle
Listen Here
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