Kohler Aegis LH775 Service Manual page 32

EFI System
Engine Misses,
Hesitates, or Stalls
Under Load
Low Power
ELECTRICAL SYSTEM
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 a 12 VDC negative ground system,
designed to operate down to a minimum of 7.0 volts.
If system voltage drops below this level, operation of
voltage sensitive components such as ECU, fuel pump,
and injectors will be intermittent or disrupted, causing
erratic operation or hard starting. A fully charged, 12
volt battery with a minimum of 350 cold cranking amps
is important in maintaining steady and reliable system
operation. Battery condition and state of charge should
always be checked fi rst when troubleshooting an
operational problem.
Keep in mind that EFI-related problems are more
often caused by wiring harness or connections than
by EFI components. Even small amounts of corrosion
or oxidation on terminals can interfere with milliamp
currents used in system operation. Cleaning connectors
and grounds will solve problems in many cases. In
an emergency situation, simply disconnecting and
reconnecting connectors may clean up contacts enough
to restore operation, at least temporarily.
32
Fuel injector(s), fuel fi lter, fuel line, or fuel pick-up dirty/restricted.
Dirty air cleaner.
Insuffi cient fuel pressure or fuel delivery.
Vacuum (intake air) leak.
Improper governor setting, adjustment or operation.
Speed sensor malfunction.
TPS faulty, mounting problem or TPS Initialization Procedure incorrect.
Bad coil(s), spark plug(s), or wires.
Faulty/malfunctioning ignition system.
Dirty air fi lter.
Insuffi cient fuel delivery.
Improper governor adjustment.
Plugged/restricted exhaust.
One injector not working.
Basic engine problem exists.
TPS faulty or mounting exists.
Throttle plates in throttle body/intake manifold not fully opening to WOT stop (if equipped).
KohlerEngines.com
If a fault code indicates a problem with an electrical
component, disconnect ECU connector and test for
continuity between component connector terminals and
corresponding terminals in ECU connector using an
ohmmeter. Little or no resistance should be measured,
indicating that wiring of that particular circuit is OK.
An illustrated listing of numerical terminal locations is
provided below.
On LH775 Kohler liquid-cooled engines, ECU and
corresponding wiring harness provide two additional
circuits. Pin circuit 32 provides ability to control an
optional OEM electric cooling fan, switching it ON and
OFF at appropriate coolant temperatures using a relay.
Pin circuit 12 switches on when coolant temperature
is too high to operate an optional engine temperature
warning light.
66 690 07 Rev. --