Ignition System - Kohler LH630-775 Service Manual

13. Depressurize the fuel system following the
procedure in the fuel warning on page 5B.2.
Remove the two fuel rail mounting screws.
14. Clean any dirt accumulation from the sealing/
mounting area of the faulty injector(s) and
disconnect the electrical connector(s).
15. Pull the retaining clip off the top of the injector(s)
and remove from manifold.
16. Reverse the appropriate procedures to install the
new injector(s) and reassemble the engine. Use
new O-Rings any time an injector is removed
(new replacement injectors include new O-Rings).
Lubricate O-Rings lightly with oil. Torque fuel
rail and blower housing mounting screws to
3.9 N·m (35 in. lb.), and the intake manifold and
air cleaner mounting screws to 9.9 N·m
(88 in. lb.).
Injector problems due to dirt or clogging are generally
unlikely, due to the design of the injectors, the high
fuel pressure, and the detergent additives in the
gasoline. Symptoms that could be caused by dirty/
clogged injectors include rough idle, hesitation/
stumble during acceleration, or triggering of fault
codes related to fuel delivery. Injector clogging is
usually caused by a buildup of deposits on the
director plate, restricting the flow of fuel, resulting in
a poor spray pattern. Some contributing factors to
injector clogging include higher than normal
operating temperatures, short operating intervals,
and dirty, incorrect, or poor quality fuel. Cleaning of
clogged injectors is not recommended; they should be
replaced. Additives and higher grades of fuel can be
used as a preventative measure if clogging has been a
problem.

Ignition System

General
A high voltage, solid state, battery ignition system is
used with the EFI system. The ECU controls the
ignition output and timing through transistorized
control of the primary current delivered to the coils.
Based on input from the speed sensor, the ECU
determines the correct firing point for the speed at
which the engine is running. At the proper instant, it
releases the flow of primary current to the coil. The
primary current induces high voltage in the coil
secondary, which is then delivered to the spark plug.
Each coil fires every revolution, but every other spark
is "wasted."
Service
Except for removing the spark plug lead by
unscrewing it from the secondary tower (see Figure
5B-18), no coil servicing is possible. If a coil is
determined to be faulty, replacement is necessary. An
ohmmeter may be used to test the wiring and coil
windings.
Figure 5B-18. Ignition Coil.
NOTE: Do not ground the coils with the ignition
''on,'' as they may overheat or spark.
1. Disconnect the main harness connector from
ECU. Locate pins #30 and #31 in the 32 pin
connector. See page 5B.24.
2. Disconnect the connector from the relay and
locate terminal #87 in connector.
3. Using an ohmmeter set on the Rx1 scale, check
the resistance in circuits as follows: Check
between terminal #87 and pin #30 for coil #1.
Repeat the test between terminal #87 and pin #31
for coil #2.
A reading of 1.8-4.0 Ω Ω Ω Ω Ω in each test indicates that
the wiring and coil primary circuits are OK.
a. If the reading(s) are not within specified
range, check and clean connections and retest.
b. If the reading(s) are still not within the
specified range, test the coils separately from
the main harness as follows:
1. Disconnect the red and black primary
leads from the coil terminals.
2. Connect an ohmmeter set on the Rx1
scale to the primary terminals. Primary
resistance should be 1.8-2.5 Ω Ω Ω Ω Ω .
Section 5B
EFI Fuel System
5B.15
5B