Symptom/Condition, Diagnosis & Parts Information

SYMPTOM/CONDITION

Vapor Lock - Engine performance is gradually reduced in high ambient temperature or high altitude driving due to a drop in fuel pressure, which starves the engine for fuel (goes lean). Engine may not start until fuel system components cool off.

Fuel Foaming - Engine sags and/or exhibits poor performance following a hot soak restart. This condition occurs when cool incoming fuel meets the hot fuel in the carburetor fuel bowl, which creates an over rich condition. Engine will start (unloading technique may be necessary).

DIAGNOSIS

Vapor lock and fuel foaming cause similar conditions. The following are characteristics of each condition and should be observed on a fully warmed up engine. (These conditions do not affect cold engine driveability.)

Vapor Lock

^ Occurs after hot soak, prolonged idle, or highway speeds at any throttle opening.
^ Sag due to lean mixture.
^ No black smoke at tailpipe.
^ Fuel pressure drops to 0.
^ Carburetor air horn dry.
^ No accelerator pump discharge.
^ May not start until engine. cools.
^ Engine may not sustain heavy loads.

Revised part numbers, TSB 18-37-85, pages 2, 4, 7, and 8, December 8, 1986

Fuel Foaming

^ Occurs primarily after hot soak restart or prolonged idle only on medium to heavy acceleration.
^ Sag due to rich fuel mixture.
^ Black smoke at tailpipe.
^ Fuel pressure is normal.
^ Raw fuel at carburetor air horn.
^ Good accelerator pump discharge.
^ Will start immediately (unloading technique may be necessary).

PARTS REQUIRED

ORDER ONE OF THE FOLLOWING TWO PACKAGE PART NUMBERS:

1984-1985 With 15 Gallon Fuel Tank PN 4419418*
1984-1985 With 20 Gallon Fuel Tank PN 4419419*

Refer to parts lists for contents of each package.

To be ordered separately:

1 - Authorized Modification Label PN 4275086

NOTE:
IT IS IMPORTANT THAT THE SPECIFIED (FUEL TANK SIZE) APPLICATION KIT BE SELECTED. THE USE OF AN IMPROPER PART NUMBER KIT MAY CAUSE THE VEHICLE TO RUN OUT OF FUEL WELL BEFORE THE GAUGE READS EMPTY.