AM/FM Radio - Whining/Buzzing Noise
Bulletin No.: 012/95Issued: 10/31/95
Revised:
Category
F
Applicable Model/s
1991-94 Navajo
1994-95 B-Series
Subject
ELECTRICAL FUEL PUMP RADIO INTERFERENCE
DESCRIPTION
The in-tank electric fuel pump may cause a "whining" or "buzzing" noise on the vehicle's AM/FM radio. An electronic noise RFI filter is available to reduce this noise.
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.
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 RFl 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.
5. Use a jumper wire to connect the two (2) pins shown in Fig. 1 to run the fuel pump.
6. Turn the ignition key "On" with the engine off.
^ Listen for static on the radio.
If the static is present and quits when the jumper wire is removed, proceed to the REPAIR PROCEDURE section of this bulletin.
If the static is not present or continues after the jumper wire is removed, refer to the workshop manual for troubleshooting and repair instructions.
7. Install relay.
REPAIR PROCEDURE
1. Remove the fuel pump sending unit from the fuel tank. Refer to section F of the workshop manual for removal instructions.
2. Remove the negative and positive connectors from the fuel pump.
3. Cut the wires to the fuel pump 3 inches (76 mm) from the flange of the fuel pump. Discard wires. Refer to Fig. 2.
4. Connect the RFl filter connectors to the spade terminals on the fuel pump.
NOTE:
It may be necessary to shorten the fuel pump ground wire to a point closer to the fuel tank. After the ground wire is moved secure and protect the wire from corrosion. Failure to protect the wire may result in an inoperable fuel pump.
5. Cut and solder both (red and black) RFI filter wires to the wires (red and black) of the fuel sender flange.
WARNING:
SOLDER AWAY FROM TANK. USE ONLY A SOLDERING IRON FOLLOW ALL GENERAL SHOP SAFETY PRACTICES DURING THIS AND OTHER SHOP RELATED ACTIVITIES INVOLVING FUEL SYSTEMS.
6. Use heat shrink tubing to protect all soldered connections (even those made prior to this service).
NOTE:
Use approximately 2 inches (51 mm) of specified type of heat shrink tubing to cover exposed soldered connections. Shrink appropriately to prevent connection exposure.
7. Secure RFI filter to the fuel pump assembly with a plastic tie-wrap to prevent rattling.
8. Install new fuel pump flange gasket.
9. Install fuel pump assembly into fuel tank.Refer to section F of the workshop manual for installation instructions.
10. Verify that the noise is reduced.
PARTS INFORMATION
WARRANTY INFORMATION
(Applies to verified customer concerns on vehicles covered under normal warranty. Refer to the SRT microfiche for applicable warranty term information).
Warranty Type: A
Customer Comment Code: 82
Damage Code: 9W
Part Number Main Cause: ZZLO 66 950
Quantity: 1
Operation Number: YY0223RX
Labor Hours: 1.5 Hrs.