Kohler COMMAND CH18 Service Manual page 59

Section 5A
LPG Fuel Systems
Operation
In a liquid withdrawal system, the Liquefied
Petroleum Gas (LPG) is released from the bottom of
the supply tank under high pressure. Upon opening
the shut-off valve on the tank, liquid fuel travels out
through the high pressure line to the electric lock-off/
filter assembly. The lock-off opens internally when the
key switch is turned "on," permitting filtered fuel to
flow to the vaporizer. The vaporizer is mounted in the
flow of the discharged cooling air. It absorbs heat from
the cooling air and transfers it to the fuel, changing the
liquefied petroleum to a vapor or gaseous state, while
partially stepping down the fuel pressure. The gas/
vapor flows under this decreased pressure to the
regulator where it is further reduced to a usable,
regulated pressure. The regulator, activated by intake
manifold vacuum, controls fuel flow to the carburetor.
In the venturi of the carburetor, the fuel vapor is
mixed with incoming air from the air cleaner in the
correct ratio for efficient combustion.
Troubleshooting Checklist
If the engine starts hard, runs roughly, or stalls, check
the following areas.
• Make sure the LPG fuel tank is filled and shut-off
valve is fully opened.
• Make sure fuel is reaching the carburetor.
• Make sure the air cleaner element and precleaner
are clean and all components are fastened
securely.
• Make sure the ignition, governor, exhaust,
throttle, and choke control systems are all
operating properly.
• Check compression.
If engine continues to start hard, run roughly, or stall
after these checks have been made, use the following
troubleshooting guide.
Engine cranks but will not start
1. LPG fuel tank closed, low, or empty.
2. Lock-off not opening electrically, preventing fuel
flow to vaporizer.
3. Fuel filter (located inside lock-off) dirty or
blocked.
5A.2
4. Insufficient vacuum signal, regulator not opening.
a. Vacuum line between carburetor and
regulator cracked, leaking, kinked, or pinched.
b. Carburetor loose.
c. Intake manifold loose or leaking.
d. Excessive internal engine wear.
5. Faulty regulator.
a. Primary valve not opening.
b. Diaphragm spring adjustment incorrect.
c. Idle adjustment screw incorrectly set.
d. Vent(s) blocked/restricted.
6. Restricted/blocked fuel line.
7. Blocked carburetor fuel circuit.
8. Loose/leaking fuel enrichment hose (Impco
carburetor system).
Hard starting, runs roughly, or stalls at idle speed
1. LPG fuel tank low.
2. Vacuum line between carburetor and regulator
pinched, cracked, or leaking.
3. Carburetor idle speed set too low (should be at
least 1200 RPM).
4. Carburetor idle circuit restricted.
5. Dirty/restricted air cleaner.
6. Dirty/restricted lock-off filter.
7. Frozen/malfunctioning regulator. Check/adjust
primary pressure.
8. Excessive external load on engine.
9. Excessive internal wear.
10. Loose/leaking fuel enrichment hose (Impco
carburetor system).
Irregular or inconsistent idle
1. Improper operation/adjustment of regulator, idle
adjustment screw, throttle opening, and/or engine
governor.
2. Secondary valve in regulator not closing. Readjust
idle screw (couterclockwise) so valve can close
fully against seat.
3. Loose/leaking vacuum line.
4. Loose carburetor mounting and/or line
connections.
5. Damaged diaphragm(s) within regulator.
6. Debris in regulator. Flush debris from drain plug
or remove regulator from system, disassemble
body and remove debris.
7. Dirt or debris in carburetor. Remove carburetor,
disassemble and clean/service as required. If
venturi (Impco carburetor) removal is performed,
mark its orientation to the carburetor body for
proper reinstallation.
8. Loose/leaking fuel enrichment hose (Impco
carburetor system).