Fuel Pipe - Vibration Noise At Idle
CHEVROLET NUMBER: 87-T-80SECTION: 6C - Engine Fuel
DATE: March, 1987
SUBJECT: FUEL PIPE VIBRATION NOISE AT IDLE
MODELS: 1987 R/V TRUCKS EQUIPPED WITH 5.0L (VIN CODE H), 5.7L (VIN CODE K), 4.3L
(VIN CODE Z) OR 7.4L (VIN CODE N) ENGINES
Some 1987 R/V models equipped with TBI engines may have a condition where the fuel feed and return pipe assemblies have been mispositioned while the vehicle was being built. As a result, the pipes contact body sheet metal, causing an unacceptable injector pulse (buzzing) noise inside the truck near the dash or the floor pan at low idle speeds. This condition can be repaired using the following procedures.
FIGURE 1 - FUEL PIPE FEED INSPECTION:
SERVICE PROCEDURES
5.0L OR 5.7L ENGINES
1. Remove the air cleaner assembly.
2. Inspect the fuel feed pipe (Figure No. 1) routing. The pipe is routed near an intake manifold vacuum boss on the rear manifold runner. Contact at this point pushes the pipe into the body dash cowl panel or transmission tunnel. If pipe contact is evident, reposition the pipe away from the vacuum boss. It should not be necessary
to disconnect or unclip the pipes to reposition them.
3. Reinstall the air cleaner and retest the truck.
FIGURE 2 - INSPECT FUEL PIPES:
FIGURE 3 - INSPECT FUEL PIPES:
4.3L AND 7.4L ENGINES
1. Remove the air cleaner assembly.
2. Inspect the fuel pipes as they pass near the floor pan and the dash cowl panel (Figures No. 2 and No. 3). The pipes must have 1/2" clearance between the floor pan and dash cowl panel. If the pipes contact the floor pan or dash cowl panel, reposition the pipes away from the floor pan or dash cowl panel. It may be necessary to raise the truck to gain access to the pipes as they pass near the floor pan. It should not be necessary to disconnect or unclip the pipes to reposition them.
3. Reinstall the air cleaner and retest the truck.
FIGURE 4 - REPOSITION OF THE INTERMEDIATE FEED:
ALL ENGINES WITH TBI
It may be necessary to reposition the intermediate feed and/or retum pipes mounted on the frame (Figure No. 4) to eliminate contact with the floor pan or transmission tunnel. Reposition the pipes as necessary. Labor time for this operation is 0.2 hrs. Add 0.1 hr. if necessary to raise the vehicle. Use Labor Op L0100.