SLOW RESUME RESPONSE DIESEL DRILL OUT VACUUM RESTRICTOR

MODELS: 1983 C-K OR G TRUCKS WITH 6.2L DIESEL ENGINES

Some 1983 C, K or G trucks equipped with a 6.2L diesel engine and cruise control may exhibit either of the following conditions when activating the cruise control.

Condition 1

Upon releasing the set/coast button at a desired speed, the vehicle speed may drop approximately 3-4 mph. The vehicle speed then gradually in- creases to the desired setting. If the vehicle is equipped with an automatic transmission, a downshift may occur and hold until the set speed is reached. Following this cycle, the cruise control operates normally.

Condition 2

Upon releasing the set/coast button at a desired speed, the vehicle speed drops approximately 34 mph and holds this lower than desired speed until the operator initiates a change.

These conditions may be caused by an over restrictive orifice in the vacuum line between the servo and the vacuum pump.

Cruise controls that may require a minor modification to their in-line vacuum orifice are easily identified by the orifice's natural color (beige). In- line orifices that have been updated are black in color.

If a vehicle has a natural colored orifice and displays either of the described conditions, the condition may be corrected by increasing the orifice diameter to 1.58 mm. (.0625 in.). Use caution when drilling the orifice as it may be easily destroyed.

Note: The orifice is located in the vacuum line between the servo and the vacuum pump. It also serves as a hose adapter to join two different diameter hoses utilized in the system.

It is important that the orifice assembly is removed from both hoses prior to drilling.

After drilling, remove any chips that may be trapped in the orifice assembly. This step is very important. Chips may contaminate the servo, making it inoperative.

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.