Table of Contents
Advertisement
Typical electronic fuel injection (EFI) system and related
components include:
● Electric fuel pump.
● Fuel fi lter.
● Fuel rail.
● Fuel line(s).
● Fuel injectors.
● Fuel pressure regulator.
● Throttle body/intake manifold.
● Electronic control unit (ECU).
● Ignition coils.
● Coolant temperature sensor.
● Throttle position sensor (TPS).
● Crankshaft position sensor.
● Oxygen sensor.
● Temperature/Manifold Absolute Pressure (TMAP)
Sensor.
● Wire harness assembly & affi liated wiring.
● 10 amp fuse (battery power).
● 10 amp fuse (ignition switch).
● 30 amp fuse (charging system).
● 10 amp fuse (fuel pump relay).
● Malfunction indicator light (MIL)-optional.
FUEL RECOMMENDATIONS
Refer to Maintenance.
FUEL LINE
Low permeation fuel line must be installed on all Kohler
Co. engines to maintain EPA and CARB regulatory
compliance.
OPERATION
NOTE: When performing voltage or continuity tests,
avoid putting excessive pressure on or against
connector pins. Flat pin probes are
recommended for testing to avoid spreading or
bending terminals.
EFI system is designed to provide peak engine
performance with optimum fuel effi ciency and lowest
possible emissions. Ignition and injection functions
are electronically controlled, monitored and continually
corrected during operation to maintain ideal air/fuel ratio.
Central component of system is Electronic Control Unit
(ECU) which manages system operation, determining
best combination of fuel mixture and ignition timing for
current operating conditions.
An electric fuel pump is used to move fuel from tank
through fuel line and in-line fuel fi lter. A fuel pressure
regulator maintains a system operating pressure of 39
psi and returns any excess fuel to tank. At engine, fuel
is fed through fuel rail and into injectors, which inject
it into intake ports. ECU controls amount of fuel by
varying length of time that injectors are on. This can
range from 2 to over 12 milliseconds depending on fuel
requirements. Controlled injection of fuel occurs every
other crankshaft revolution, or once for each 4-stroke
cycle. When intake valve opens, fuel/air mixture is drawn
into combustion chamber, ignited, and burned.
66 690 14 Rev. A
ECU controls amount of fuel being injected and ignition
timing by monitoring primary sensor signals for engine
temperature, speed (RPM), and throttle position (load).
These primary signals are compared to preprogrammed
maps in ECU computer chip, and ECU adjusts fuel
delivery to match mapped values. After engine reaches
operating temperature, an exhaust gas oxygen sensor
provides feedback to ECU based upon amount of
unused oxygen in exhaust, indicating whether fuel
mixture being delivered is rich or lean. Based upon this
feedback, ECU further adjusts fuel input to re-establish
ideal air/fuel ratio. This operating mode is referred to as
closed loop operation. EFI system operates closed loop
when all three of following conditions are met:
● Engine coolant temperature is greater than 35°C
(95°F).
● Oxygen sensor has warmed suffi ciently to provide a
signal (minimum 375°C, 709°F).
● Engine operation is at a steady state (not starting,
warming up, accelerating, etc.).
During closed loop operation ECU has ability to readjust
and learn adaptive controls, providing compensation
for changes in overall engine condition and operating
environment, so it will be able to maintain ideal air/
fuel ratio. This system requires a minimum engine oil
temperature greater than 80°C (176°F) to properly
adapt. These adaptive values are maintained as long as
ECU is not reset.
During certain operating periods such as cold starts,
warm up, acceleration, high load, etc., a richer air/fuel
ratio is required and system operates in an open loop
mode. In open loop operation oxygen sensor output is
used to ensure engine is running rich, and controlling
adjustments are based on primary sensor signals and
programmed maps only. This system operates open
loop whenever three conditions for closed loop operation
(above) are not being met.
ECU is brain or central processing computer of entire
EFI system. During operation, sensors continuously
gather data which is relayed through wiring harness
to input circuits within ECU. Signals to ECU include:
ignition (on/off ), crankshaft position and speed (RPM),
throttle position, oil temperature, intake air temperature,
exhaust oxygen levels, manifold absolute pressure, and
battery voltage.
ECU compares input signals to programmed maps in
its memory to determine appropriate fuel and spark
requirements for immediate operating conditions. ECU
then sends output signals to set injector duration and
ignition timing.
ECU continually performs a diagnostic check of itself,
each of sensors, and system performance. If a fault
is detected, ECU can turn on a Malfunction Indicator
Light (MIL) (if equipped) on equipment control panel,
store fault code in its fault memory, and go into a default
operating mode. Depending on signifi cance or severity
of fault, normal operation may continue. A technician can
access stored fault code using a blink code diagnosis
fl ashed out through MIL. An optional computer software
diagnostic program is also available, see Tools and Aids.
KohlerEngines.com
EFI System
27
Advertisement
Table of Contents
