FUEL LINE KNOCK/HAMMER NOISE INSTALL EXPANSION CHAMBER P/N

FUEL LINE KNOCK/HAMMERING (Revised to Include 1988 'J' Car)

VEHICLES AFFECTED: 1987-88 'L' AND 1987-88 'J' CAR ----------------- WITH 2.8 MPFI V-6 (RPO LB6)

Some 1987-88 'L' cars and 1987-88 'J' cars with 2.8L MPFI engines may exhibit a light hammering/knocking type noise audible in the vehicle passenger compartment at ambient temperatures above -9 deg C (15 deg F). Noise condition may be noted in a cold start mode, and/or warm stabilized mode and is most apparent at engine idle.

This condition may be caused by pressure pulsations in the fuel system generated by fuel injector operation, resulting in hydraulic hammering in chassis fuel pipes.

Vehicles exhibiting this condition may be repaired by installation of a new engine fuel feed pipe - expansion chamber assembly following the service procedure in this bulletin. (See Illustration).

Part required for this installation is available from GM PARTS and is noted below:

PART NUMBER PART DESCRIPTION QUANTITY ----------- ---------------- -------- 10115810 Fuel Feed Pipe - Expansion 1 Chamber Assembly Service Procedure: ----------------- 1. Disconnect negative battery cable and remove fuel tank filler cap.

2. Relieve pressure in fuel system following shop manual procedure.

3. Disconnect fuel feed hose at engine fuel feed pipe utilizing back-up wrench on fittings.

4. Remove bolt securing engine fuel feed and return pipe bracket at cylinder head.

5. Remove oil fill cap and disconnect vacuum line and the idle air control valve electrical connector at the throttle body.

6. Disconnect fuel return pipe and then fuel feed pipe at fuel rail fittings utilizing backup wrench.

7. Position pipes to gain access to bolt securing pipe clip to engine bracket and remove bolt.

8. Remove feed pipe from clip and discard.

9. Torque fuel rail feed and return fittings to 20-26 N.m.

10. Install new fuel feed pipe-expansion chamber assembly, P/N 10115810, and insert into retaining clip.

11. Install retaining clip to engine bracket torquing bolt to 4.5-7 N.m.

12. Connect fuel feed and then fuel return pipe to fuel rail, torquing fittings to 20-26 N.m utilizing backup wrench.

13. Install engine bracket to cylinder head torquing bolt to 40-60 N.m.

14. Connect fuel feed hose to engine feed pipe. Torque fitting to 20-34 N.m utilizing backup wrench on fitting.

15. Install oil fill cap and connect vacuum line and electrical connector.

16. Connect negative battery cable and install fuel tank cap.

17. Start engine, check all connections for possible leaks and correct as required.

Use applicable Labour Operation Number and Claim .7 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.