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 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.

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

Three different kits are required with the various fuel gauges and fuel tanks used from 1981 through 1987.

Order one of the respective kit part numbers outlined below:

1981-1983 Models (W/Bi-Metallic Fuel Gauge) PN 4364380
1984 Models (W/Magnetic Fuel Gauge) PN 4364381
1985-1987 Models (W/Magnetic Fuel Gauge) PN 4364382

See detailed parts list attached.

Must order separately:

1 Authorized Modification Label PN 4275086