REDUCE HIGH AMBIENT COLD START DRIVEABILITY (PUMP REPAIR)

y DRIVEABILITY: HIGH AMBIENT COLD START DRIVEABILITY

1986-87 SAFARI WAGON, FIREBIRD AND GRAND PRIX MODELS WITH 5.0L ENGINE LG4 (VIN CODE H)

"This bulletin supersedes bulletin 87-6(Gasoline)-90, dated 5/88. This bulletin is being revised to delete the word reduced from the title and change the word reduced to regarding in the first paragraph."

Some 1986-87 passenger cars equipped with LG4 (VIN Code H) engines may experience customer comments regarding driveability during the first few minutes of operation after startup, following an extended soak (6 hours or more) at relatively high ambient temperatures.

This condition may be the result of leanness during this type of operation. Typical symptoms of leanness are idle roughness and hesitation or sag on tip- in. In some instances, the condition may be addressed by performing the following service procedures.

Parts Required

1 P/N 17083343 Accelerator pump discharge spring 1 P/N 17083344 Accelerator pump assembly

Service Procedure

A. Install the new accelerator pump and discharge spring as follows:

1. Disconnect the negative battery cable. 2. Remove the air cleaner. 3. Remove the carburetor air horn. (Refer to Section 6C1 of the Service Manual if details of disassembly are needed.) 4. Remove the solenoid adjusting screw plug from the airhorn. 5. Remove the solenoid plunger, air horn gasket, pump assembly, metering rods, and float bowl insert. 6. Count and record the number of turns to the solenoid adjusting screw to lightly bottom the mixture control solenoid. 7. Remove the mixture control solenoid assembly. 8. Remove the float and needle. 9. Remove the accelerator pump discharge plug. 10. Install accelerator pump discharge spring, P/N 17083343. 11. Reinstall the accelerator pump discharge plug. 12. Remove the existing accelerator pump and install P/N 17083344 accelerator pump. 13. Reinstall the float and needle. (Hook needle clip over the crossbar facing seat. Do not hook through holes in float lever). 14. Reinstall the mixture control solenoid. 15. Reinstall the solenoid adjusting screw and turn it to lightly bottom the solenoid, then back it out the number of turns recorded during disassembly. 16. Reinstall the float bowl insert, metering rods, pump assembly, air horn gasket, and solenoid plunger. 17. Reinstall the air horn. 18. Reinstall the solenoid adjusting screw plug. 19. Reinstall the air cleaner.

B. Adjust the choke stat lever (also known as "solid makeup") per the procedure on page 6C1-26 (figure 6C1-53) of the 1987 Safari Wagon or Firebird Service Manual. Specifications for these and the other adjustments to follow are given on page 6C1-30 figure 6C1-61.

C. Adjust the vacuum brake per procedure on page 6C1-28 (see figure 6C1-028557).

D. Reset the idle mixture needles and adjust the air bleed valve to the correct dwell at idle per procedures on pages 6E-C2B-8 and 9.

E. Reconnect the negative battery cable.

Warranty Information

Labor Operation: T1341

Labor Time : 2.0 Hours

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.