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5A.3
Section 5A
LPG Fuel Systems
5A
Engine stalls during operation
1. No fuel.
2. Faulty lock-off or blocked filter.
3. Improper governor setting.
4. Damaged diaphragms within regulator.
5. Vacuum line leaking, loose, or pinched.
6. Restricted fuel line.
7. Loose/leaking fuel enrichment hose (Impco
carburetor system).
Low power
1. Air cleaner or exhaust system dirty/restricted.
2. Low fuel.
3. Rich gas condition (flooding) through regulator.
a. Dirty/restricted valves in regulator.
b. Damaged primary diaphragm in regulator.
4. No fuel.
a. Electric lock-off not opening, filter blocked, or
restriction within fuel line.
b. Leaking, loose, or cracked vacuum line from
carburetor to regulator.
c. Leaking, or loose intake system components.
d. Regulator primary valve not opening.
e. Secondary, or vacuum lock-off diaphragm
within regulator leaking.
f. Low pressure rubber hose kinked.
g. Frozen regulator.
5. Improper ignition timing.
6. Loose/incorrect throttle lever/clamp bracket
positioning.
7. Loose or incorrectly positioned high speed throttle
plate stop.
Engine runs lean
1. Electrical problem causing intermittent lock-off
operation, or lock-off is faulty.
2. Filter in lock-off dirty or restricted.
3. Restriction in fuel system.
4. Idle holes plugged; dirt in fuel delivery channels.
5. Carburetor fuel circuit restriction.
6. Loose/leaking fuel enrichment hose (Impco
carburetor system).
High fuel consumption
1. Fuel leak. Check lines, connections, and system
components for leaks with soapy water. Fix any
leaks immediately.
2. Incorrectly set regulator, or leakage from valves in
regulator. Readjust, service, or replace regulator
as required.
3. Dirty air cleaner or precleaner.
4. Choke plate in carburetor not opening completely.
LPG Carburetor Adjustments
General
The LPG carburetor and regulator are designed to
deliver the correct fuel-to-air mixture to the engine
under all operating conditions. The high and low idle
fuel mixture settings are preset at the factory, and
cannot be adjusted. These engines are equipped with
an Impco or Nikki carburetor. See Figure 5A-2 and
5A-3. Although both carburetors function similarly,
each is unique and should not be interchanged.
Figure 5A-2. Impco Carburetor.
Figure 5A-3. Nikki Carburetor.
Impco carburetors also incorporate the use of an
external ‘‘Load Block’’ assembly, which controls the
final fuel flow to the carburetor for all throttle positions
except idle. See Figure 5A-2. Calibrated and flow-
matched to the carburetor, it functions similarly to
preset fuel mixture settings in other carburetors. The
load block assembly is not available separately, nor is
any internal servicing permitted or possible. If a
problem is encountered and determined to be caused
by the load block, the carburetor should be replaced.
Rear Plug
with Sealing
Washer
Choke Plate/Shaft Assembly
Fuel Inlet
Plastic Bushing
Transfer
Chamber
Cover
Vacuum Port
Idle Speed
Adjusting Screw
Load Block Assembly
Fuel Enrichment
Hose
Fuel Inlet
Venturi
Retaining
Screw
Idle Speed
Adjusting Screw