FUEL LINE KNOCK-COLD FUEL THERMAL DISC/FUEL RETURN LINE

Some 1982 and 1983 "A" and "X" cars with 2.8L V6 engines may exhibit fuel line knock when cold. The noise is usually heard inside the car, and is more pronounced when the vehicle is cold but may still be present after vehicle reaches operating temperature. In most cases, the noise can be temporarily eliminated by pinching off the fuel pump return flex hose.

To alleviate this condition, install thermal disc, P/N 14077716, in the fuel return line. The thermal disc shuts the return line in ambients below 60 DEG (15.5 DEG C) and when open has a restrictor orifice of 1.5mm. The valve is marked for directional flow, tank towards tank and pump towards fuel pump.

Installation Procedure

1. Locate fuel return hose in engine compartment, cut the flex hose two inches from the end attached at the transmission. Remove approximately 1/2" of hose from the hose attached to the chassis pipe. Note if the section of hose has a restrictor installed the hose and restrictor should be discarded and replaced with a new piece of hose (GM 6198M) 8 1/2" long (refer to Figure 1).

2. Remove and discard the hose on the thermal valve (P/N 14077716) and install according to flow direction as previously mentioned.

3. Install hose clamps, P/N 1619412, and torque to specification (25 in. lbs.). Refer to Figure 1. Two clamps required at thermal valve and one clamp required

4. Check for clearance between the thermal valve and the fuel feed hose. If clearance is not approximately 1/2", carefully bend the return pipe up-ward to achieve this clearance.

Labor Operation Number: J6300

Labor Time : .3 hour

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.