Fuel Pump; Fuel Pressure Regulator Details - Kohler command pro ECH749 Service Manual

EFI SYSTEM-BOSCH
3. Disconnect secondary lead from spark plug.
Connect an ohmmeter set on Rx10K scale
between spark plug boot terminal and red
primary terminal. Secondary resistance should
be 13,000-17,500 Ω.
4. If secondary resistance is not within specifi ed
range, unscrew spark plug lead nut from coil
secondary tower and remove plug lead.
Repeat step b. 3, testing from secondary
tower terminal to red primary terminal. If
resistance is now correct, coil is good, but
spark plug lead is faulty, replace lead. If step
b. 2 resistance was incorrect and/or
secondary resistance is still incorrect, coil is
faulty and needs to be replaced.
Wiring harness used in EFI system connects electrical
components, providing current and ground paths for
system to operate. All input and output signaling occurs
through a special all weather connector that attaches
and locks to ECU.
Condition of wiring, connectors, and terminal
connections is essential to system function and
performance. Corrosion, moisture, and poor connections
are more likely cause of operating problems and system
errors than an actual component.

Fuel Pump

Fuel pumps are non-serviceable and must be replaced
if determined to be faulty. If a fuel delivery problem
is suspected, make certain pump is being activated
through relay, all electrical connections are properly
secured, fuses are good, and a minimum of 7.0 volts
is being supplied. If during cranking, voltage drops
below 7.0 volts, a reduction of fuel pressure may occur
resulting in a lean starting condition. If required, testing
fuel pump and relay may be conducted.
1. Connect black hose of Pressure Tester (part of EFI
Service Kit, see Tools and Aids) to test valve in fuel
rail. Route clear hose into a portable gasoline
container or equipment fuel tank.
2. Turn on key switch to activate pump and check
system pressure on gauge. If system pressure of 39
psi ± 3 is observed, relay, fuel pump, and regulator
are working properly. Turn key switch off and
depress valve button on tester to relieve system
pressure.
a. If pressure is too high, and regulator is outside
tank (just down line from pump), check that return
line from regulator to tank is not kinked or
blocked. If return line is good, replace regulator
(see Regulator on page).
b. If pressure is too low, install in-line ''T'' between
pump and regulator and retest pressure at that
point. If it is too low there also, replace fuel pump.
3. If pump did not activate (step 2), disconnect plug
from fuel pump. Connect a DC voltmeter across
terminals in plug, turn on key switch and observe if a
minimum of 7 volts is present. If voltage is between
7 and 14, turn key switch off and connect an
ohmmeter between terminals on pump to check for
continuity.
70
a. If there was no continuity between pump
terminals, replace fuel pump.
b. If voltage was below 7, test wiring harness and
relay as covered in Electrical Relay.
4. If voltage at plug was good, and there was continuity
across pump terminals, reconnect plug to pump,
making sure you have a good connection. Turn on
key switch and listen for pump to activate.
a. If pump starts, repeat steps 1 and 2 to verify
correct pressure.
b. If pump still does not operate, replace it.

Fuel Pressure Regulator Details

A Pressure Regulating
C Diaphragm
E
Fuel Chamber
G Return Port (to tank)
I
Depending on application, regulator may be located in
fuel tank along with fuel pump, or outside tank just down
line from pump. Regulator is a sealed, non-serviceable
assembly. If it is faulty, it must be separated from base/
holder assembly and replaced as follows:
1. Shut engine off, make sure engine is cool, and
disconnect negative (-) battery cable.
2. Depressurize fuel system through test valve in fuel
rail.
3. Access regulator assembly as required and clean
any dirt or foreign material away from area.
4. External Regulator-
a. Remove screws securing mounting bracket to
regulator housing. Remove O-Ring and pull
regulator out of housing.
b. Remove snap ring and remove regulator
from base/holder.
KohlerEngines.com
A
B
I
H
F
G
B Pressure Regulating
Spring
D
F
H
Valve
C
D
E
Chamber
Valve Seat
Outlet Port
(to fuel rail)
Inlet Port
24 690 01 Rev. K