Article 932 - Cold and/or Warm Engine Stall or Hesitation on Acceleration

TSB #50 - November 4, 1966
(1967 Units with 4300 Design Carburetor Built Prior to Approximately December 1, 1966 - 289-4V, 390-4V non-GT, 428-4V)


A service modification kit has been released to correct customer complaints of stall or hesitation on subject units built prior to approximately December 1, 1966. This condition can occur with a warm or cold engine. Revised 4300 design carburetor models which contain the modifications outlined in this article can be readily identified by the presence of the accelerator pump lever return spring illustrated in Illus. S1131.

This service modification kit (Part Number C7AZ-9D814-A, Class "A") contains the necessary parts to modify the accelerator pump linkage and revise the choke calibration. The following procedure must be used to properly apply these modifications:
    1. Remove the accelerator pump lever pivot pin and discard the pump lever, pump rod and "C" retainer. (Illus. S1124)
    2. Remove the vent valve lever (Illus. S1129)
    3. Place the revised pump lever between the casting supports and measure the total lever to support clearance. Adjust this total clearance to .010 inch by bending the supports with pliers (Illus. S1130)
    4. (Standard transmission units only.) Attach the spring bracket included in this kit to the carburetor base using the screw and lockwasher supplied. (Illus. S1131) Automatic transmission equipped units already contain this bracket to retain the transmission kickdown return spring.
    5. Install the vent valve lever, revised pump lever, pivot pin and "E" retainer using the #2 (center) pump adjustment hole. (Illus. S1131)
    6. Install the revised pump rod, flat washer and return spring as shown in Illus. SI 131. Be sure the long end of the spring is installed in the pump rod.
    7. With the throttle at curb idle, adjust the fuel bowl vent gap to 1/16 inch. Bend the vent valve lever to obtain this clearance. (Illus. S1132) CAUTION: DO NOT BEND THE VENT ARM TO OBTAIN PROPER ADJUSTMENT.
    8. Install the revised choke cover (Model "BO") on 390-4V and 428-4V automatic transmission units only and adjust this replacement to an "index"
    setting. (Discard the revised choke cover included in the kit when performing this modification to other carburetor models).
    9. Start the engine with a tachometer connected and check the choke fast idle engine RPM. (Be sure the choke fast idle adjustment screw is on the intermediate step of the plastic fast idle cam.)
    BASE ENGINE - The fast idle speed must be 1200 RPM
    THERMACTOR ENGINE - The fast idle speed must be 1400 RPM
    10. Reinstall the air cleaner to complete this carburetor modification.
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Illus. S1129
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Illus. S1130
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Illus. S1131
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Illus. S1132


WARRANTY STATUS: REIMBURSABLE
Oper: SP9510-B-67 Install Accelerator Pump Modification Kit
Time: 0.4 Hrs. (Add 0.2 Hrs. to replace choke cover on 390-4V and 428-4V automatic transmission equipped units only)