7324 690 01 Rev. K KohlerEngines.com
EFI SYSTEM-BOSCH
Engine starts hard
or fails to start
when hot
Faulty spark plugs.
Fuel pump not running.
Fuel pressure low.
Insuffi cient fuel delivery.
TPS offset incorrect (Initialization).
Speed sensor loose or faulty.
TPS faulty.
Engine temperature sensor faulty.
Faulty injectors.
Engine stalls or
idles roughly (cold
or warm)
Faulty spark plugs.
Insuffi cient fuel delivery.
TPS offset incorrect.
TPS faulty.
Faulty engine temperature sensor.
Faulty injectors.
Engine misses,
hesitates, or stalls
under load
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.
Low Power
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 so equipped).
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.
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, for each
style of ECU/connector is provided on pages 63, 65, and
67.
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