Kohler Command PRO EFI ECH749 [94/180] Efi system bosch
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Kohler Command PRO EFI ECH749 [94/180] Efi system bosch

Kohler Command PRO EFI ECH749 [94/180] Efi system bosch
EFI SYSTEM-BOSCH
94
24 690 01 Rev. OKohlerEngines.com
A high-voltage, solid-state, battery ignition system is
used with EFI system. ECU controls ignition output and
timing through transistorized control of primary current
delivered to coils. Based on input from speed sensor,
ECU determines correct fi ring point for speed at which
engine is running. At proper instant, it releases fl ow of
primary current to coil. Primary current induces high
voltage in coil secondary, which is then delivered to
spark plug. Each coil fi res every revolution, but every
other spark is "wasted".
An electric fuel pump is used to transfer fuel in EFI
system. Depending on application, pump may be inside
fuel tank, or in fuel line near tank. Pumps are rated for
a minimum output of 25 liters per hour at 39 psi. Pumps
have an internal 60-micron fi lter. In addition, in-tank
style pumps will have a pre-fi lter attached to inlet. In-line
pump systems may also have a fi lter between tank and
pump on pickup/low pressure side.
When key switch is turned “ON” and all safety switch
requirements are met, ECU, through relay activates
fuel pump, which pressurizes system for start-up. If key
switch is not promptly turned to start position, engine
fails to start, or engine is stopped with key switch “on”
(as in case of an accident), ECU switches off pump
preventing continued delivery of fuel. In this situation,
MIL will go on, but it will go back off after 4 cranking
revolutions if system function is OK. Once engine is
running, fuel pump remains on.
Fuel pressure regulator assembly maintains required
operating system pressure of 39 psi ± 3. A rubber-
fi ber diaphragm divides regulator into two separate
sections; fuel chamber and pressure regulating chamber.
Pressure regulating spring presses against valve holder
(part of diaphragm), pressing valve against valve seat.
Combination of atmospheric pressure and regulating
spring tension equals desired operating pressure. Any
time fuel pressure against bottom of diaphragm exceeds
desired (top) pressure, valve opens, relieving excess
pressure, returning excess fuel back to tank.
Fuel rail is a formed tube assembly that feeds fuel to
top of injectors. Tops of injectors fi t into formed cups
in fuel rail. When rail is fastened to manifold, injectors
are locked into place. A small retaining clip provides a
secondary lock. Incorporated into fuel rail is a pressure
relief/test valve for testing operating pressure or relieving
fuel system pressure for servicing. Fuel supply line is
attached to barbed end of fuel rail with an Oetiker hose
clamp.
EFI engines have no carburetor, so throttle function
(regulate incoming combustion airfl ow) is incorporated in
intake manifold assembly. Manifold consists of a one-
piece aluminum casting which also provides mounting
for fuel injectors, throttle position sensor, fuel rail, air
baffl e, idle speed screw, and air cleaner assembly.
Idle speed is only adjustment that may be performed on
EFI system. Standard idle speed setting for EFI engines
is 1500 RPM, but certain applications might require
a diff erent setting. Check equipment manufacturer’s
recommendation.
For starting and warm up, ECU will adjust fuel and
ignition timing, based upon ambient temperature, engine
temperature, and loads present. In cold conditions,
idle speed will probably be higher than normal for a
few moments. Under other conditions, idle speed may
actually start lower than normal, but gradually increase
to established setting as operation continues. Do not
attempt to circumvent this warm up period, or readjust
idle speed during this time. Engine must be completely
warmed up, in closed loop operating mode for accurate
idle adjustment.
IMPORTANT NOTES!
● Cleanliness is essential and must be maintained at all
times when servicing or working on EFI system. Dirt,
even in small quantities, can cause signifi cant
problems.
● Clean any joint or fi tting with parts cleaning solvent
before opening to prevent dirt from entering system.
● Always depressurize fuel system through fuel
connector on fuel pump module before disconnecting
or servicing any fuel system components.
● Never attempt to service any fuel system component
while engine is running or ignition switch is ON.
● Do not use compressed air if system is open. Cover
any parts removed and wrap any open joints with
plastic if they will remain open for any length of time.
New parts should be removed from their protective
packaging just prior to installation.
● Avoid direct water or spray contact with system
components.
● Do not disconnect or reconnect ECU wiring harness
connector or any individual components with ignition
on. This can send a damaging voltage spike through
ECU.
● Do not allow battery cables to touch opposing
terminals. When connecting battery cables attach
positive (+) cable to positive (+) battery terminal fi rst,
followed by negative (-) cable to negative (-) battery
terminal.
● Never start engine when cables are loose or poorly
connected to battery terminals.
● Never disconnect battery while engine is running.
● Never use a quick battery charger to start engine.
● Do not charge battery with key switch ON.
● Always disconnect negative (-) battery cable before
charging battery, and also unplug harness from ECU
before performing any welding on equipment.
Initial Starting/Priming Procedure
Important: EFI fuel system must be purged of air
(primed) prior to initial start up, and/or any time system
has been disassembled or fuel tank run dry.
1. Locate electronic control unit (ECU) for EFI system.
Check part number on end. If Part No. is 24 584 28
or higher, ECU has a built-in priming feature.
a. Turn key switch to “ON/RUN” position. You will
hear fuel pump cycle on and off . When fuel pump
stops cycling (approximately one minute), system
is primed; start engine.

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