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14-4
FUEL SYSTEM-DIAGNOSIS
Condition
Possible Cause
Correction
(c) Choke vacuum diaphragm inoperative or
(d) Choke Vacuum passage blocked or leaking.
(c) Repair or replace the vacuum unit.
(d) Open the passage. Correct any leaks.
misad justed.
CARBURETOR RICH
(a) Incorrect gasket or gasket installation between
carburetor and intake manifold.
EXCESSIVE STALLS AFTER COLD START
CHOKE SYSTEM LEAN
(a) Check items under "Poor Starting-Choke
(b) Choke vacuum diaphragm adjustment lean.
Valve Fails to Close."
ENGINE
OUTPUT LOW
(a) Fast idle speed low.
(b) Fast idle cam position adjustment incorrect.
(c) Engine lubrication oil of incorrect viscosity.
CARBURETOR LEAN
(a) Curb
idle
very lean.
(b) Air leak bypassing the carburetor.
POOR COLD ENGINE STARTING
INCORRECT PROCE-
DURE
(a) Throttle must be opened to free choke system.
Best position for all temperatures and all con-
ditions is
%
open.
CHOKE VALVE
FAILS
TO
CLOSE
specified.
(a) Choke thermostat adjustment leaner than
(b) Choke thermostat corroded such that it has
cracked and distorted lean.
(c) Choke linkage, shaft or related parts corroded,
bent or dirty such that the system is not entirely
free to move from the open to the closed posi-
tion.
(d) Choke valve improperly seated.
(e) Air cleaner interferes with choke shaft or
(f) Air cleaner gasket interferes with choke valve
linkage.
or linkage.
LOW ENGINE OUTPUT
(lO°F or lower)
(a) Engine lubricating oil of incorrect viscosity.
(b)
Valve clearing incorrect.
(c) Choke thermostat adjustment incorrect, rich.
ENGINE RUNS LEAN,
FIRST
HALF
MILE
CHOKE LEAN
(a) Check items under (Poor Starting).
(b) Diaphragm adjustment lean.
ENGINE RUNS LEAN AFTER HALF
MILE
ENGINE
HEAT
INSUFFICIENT
(a) Heat valve stuck open.
(b) Heat valve thermostat distorted.
(c) Heat valve failed within exhaust. See engine
section for proper diagnosis.
(d) Water temperature sub-normal.
(a) Replace or correct.
(b) Adjust to Specification.
(a) Adjust to specification.
(b) Adjust to specification.
(c) Recommend 5W-20.
(a) Adjust the idle mixture.
(b) Correct the air leak.
(a) Instruct owner in correct procedure for starting.
(a) Adjust the choke thermostat.
(b) Replace the choke thermostat assembly.
(c) Repair, clean or replace linkage as required.
(d) Relocate the choke valve.
(e) Rotate cleaner to correct position, and tighten.
(f) Install gasket properly.
(a) Recommend 5W-20.
(b) Adjust tappets.
(c) Adjust to correct setting.
(a) See "Choke Valve Fails to Close."
(b) Adjust to specification.
(a) Free up with solvent.
(b) Replace thermostat.
(c) Replace heat valve.
(d) Test engine. Replace if necessary.
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