Fuel Line - Knock/Hammering
Number: 87-175Section: 6C
Date: JULY, 1987
Subject: FUEL LINE KNOCK/HAMMERING
Model and Year: 1987 CELEBRITY WITH 2.8L MPFI
V-6 (RPO LB6)
TO: ALL CHEVROLET DEALERS
Some 1987 Celebrity models with 2.8L MPFI engines may exhibit a light hammering/knocking type noise audible in the vehicle passenger compartment at ambient temperatures above 15 degrees Fahrenheit. 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 GMSPO and is noted below:
PART NUMBER PART DESCRIPTION QUANTITY
10087551 Fuel Feed Pipe - Expansion
Chamber Assembly 1
Service Procedures:
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 backup 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. Check torque of fuel rail feed and return fittings for possible looseness from performing Step 6. Torque specification for both fittings is 20-26 N-m.
10. Install new fuel feed pipe-expansion chamber assembly, P/N 10087551 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.
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.
Labor Operation Number: T1193
Labor Time: .7 Hour