B4000 4WD V6-4.0L OHV (1995)
Radio/Stereo Noise Filter: All Technical Service Bulletins
Audio System - Electrical Noise from Fuel Pump
Bulletin No.: 023/96
Issued: 09/09/96
Revised:
Category
F
Applicable Model/s
1991 - 94 Navajo
1994 - 96 B-Series
Subject:
ELECTRICAL FUEL PUMP RADIO INTERFERENCE
NOTE:
This bulletin was originally released as Cat F, 012/95. Make the necessary reference to this bulletin in your 1995 Service Bulletin Book
DESCRIPTION
The in-tank electric fuel pump may cause a "whining" or "buzzing" noise on the vehicle's AM/FM radio. This concern may be aggravated by the fuel
pump ground wire acting as an antenna.
The vehicle may require installation of an electronic noise RFI filter and the fuel pump ground may need shortened.
If a customer complains of this noise, inspect the vehicle's audio system according to the procedure in this bulletin (TEST PROCEDURE) before
installing the RFI filter and shortening the fuel pump ground wire.
TEST PROCEDURE
Fuel pump radio noise is relatively constant and changes only slightly with engine RPM. If the radio noise changes constantly with the engine RPM, the
fuel pump is not the cause of the problem and the RFI filter will not effectively reduce the noise.
The following procedure will help determine if the fuel pump is the cause of the radio noise.
1.
Turn the key to the "Accessory" position and turn the radio on.
^
Tune the radio to a "known" strong station.
2.
Turn the key to the "Run" position (do not start the engine).
3.
The fuel pump should run for approximately one (1) second with the key in the "Run" position.
^
Listen for radio noise.
If the noise is present when the fuel pump is running and stops when the fuel pump stops, the noise is being generated by the fuel pump. Install
the RFI filter according to the instructions below.
If the noise is not present when the fuel pump is running or is constant even when the fuel pump quits running, the noise source may not be the
fuel pump. Proceed to step 4 for further diagnostics.
4.
Remove the fuel pump relay.
