Fuel Line - Knocking/Hammering Noise
88cad01Bulletin No. T-88-92
File in Group 6C
Number 114
Corp. Ref. No. 836301R
Date Feb. '88
SUBJECT: FUEL LINE KNOCK/HAMMERING
MODELS AFFECTED: 1987-1988 CIMARRONS
Some 1987-1988 Cimarrons may exhibit a light hammering or knocking type noise audible in the vehicle passenger compartment. This noise is usually experienced at ambient temperatures above 15~ F and is most apparent at engine idle. It may be noted during a cold start and/or when the engine is warm and stabilized.
This condition may be caused by pressure pulsations in the fuel system due to fuel injector operation. The pulsations result in a hydraulic hammering in the chassis fuel pipes.
To repair this condition, install a new engine fuel feed pipe having an expansion chamber assembly using the service procedure described below. The fuel feed pipe is available from GMSPO using P/N 10115810.
FIGURE 1 - FUEL FEED PIPE WITH EXPANSION CHAMBER ASSEMBLY:
Service procedure (refer to Figure 1):
1. Disconnect negative battery cable and remove fuel tank filler cap.
2. Relieve pressure in fuel system following Service Manual procedure in Section 6E3-C2, "Fuel Pressure Relief Procedure".
3. Disconnect fuel feed hose at engine fuel feed pipe. Use a backup wrench on all fittings.
4. Remove the bolt securing the engine fuel feed and return pipe bracket at the cylinder head.
5. Remove the oil fill cap and disconnect the vacuum line and the idle air control valve electrical connector at the throttle body.
6. Disconnect the fuel return pipe and then the fuel feed pipe at the fuel rail fittings. Use a backup wrench.
7. Position both pipes to gain access to the bolt securing the pipe clip to the engine bracket. Remove the bolt.
8. Remove the feed pipe from the clip and discard pipe.
9. With the fuel pipes removed, torque the fuel rail feed and return fittings to 23 N-m (17 ft. lbs.).
10. Install the new fuel feed pipe assembly, P/N 10115810, into the pipe retaining clip.
11. Install retaining clip to engine bracket. Torque bolt to 6 N-m (50 in.lbs.).
12. Connect the fuel feed and then the fuel return pipe to fuel rail. Torque fittings to 23 N-m (17 ft.lbs.) using a backup wrench.
13. Install the engine bracket to cylinder head. Torque bolt to 50 N-m (35 ft.lbs.).
14. Connect the fuel feed hose to the engine feed pipe. Torque fitting to 27 N-m (20 ft.lbs.) using a backup wrench.
15. Reconnect vacuum line and electrical connector to the throttle body and reinstall the oil fill cap.
16. Reconnect the negative battery cable and install fuel tank cap.
17. Start engine and check all connections for leaks. Correct as required.
For warranty purposes, use Labor Operation T6263 at .7 hour.