FUEL TANK SENDER WHINE/WHISTLING NOISE

VEHICLES AFFECTED: 1988 CHEVROLET CAPRICE W/4.3L LB4 (VIN CODE Z)

Some 1988 Chevrolet Caprices with V-6 engines (RPO LB4) may exhibit a "whining/whistling" type noise coming from the rear of the vehicle. This condition is most apparent when the engine is shut down after extended city stop and go driving, or operation at high ambient temperatures.

To reduce the possibility of this occurring an interim production change to the evaporative emission control system (EECS) was implemented on dates indicated below by assembly plant, with applicable VIN breakpoints:

Plant Implementation Date VIN Breakpoint ----- ------------------- ---------------- Arlington April 29, 1988 JR176762

Lakewood May 19, 1988 JA160363

This change terminated usage of an in-tank pressure control valve which was part of the fuel tank sender assembly, and initiated usage of an underhood externally mounted tank pressure control valve.

Service fuel tank sender assemblies available from GM Parts are of the second design configuration without the in-tank pressure control valve feature. When replacement of fuel tank sender assembly is required on vehicles assembled prior to the above indicated breakpoints, it will be necessary to install a fuel tank pressure control valve kit,P/N 10113082, in the existing hose assembly connecting the vapor carbon canister to the evaporative emission chassis pipe. The instructions for this installation are included in the fuel tank sender assembly service kit, P/N 25026719.

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.