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post #1 of (permalink) Old 04-24-2000, 06:39 PM
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Electrical Buzz

My 95 Bronco XLT, 351M, is making a electrical buzzing sound. It seems to be coming from the transfer case or fuel cell. You can really hear it if you stand behind it. Any help on trying to figure out what is going on, will be appreciated. Thanks!

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post #2 of (permalink) Old 04-24-2000, 08:06 PM
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Re: Electrical Buzz

When does it make this noise? Is the engine on or off?

Based on the location that you described, it could be a problem with the fuel pump. There is one located on the inside frame, drivers side, near the transfercase (just in front of maybe?). This should normally trun on for a moment when the key is truned to the "on" position. Normally you can hear it quietly run if you turn the key on, but don't start the truck. Maybe there is a problem with the pump's motor or the electrical connection to it... check the condition of the wires and motor.


post #3 of (permalink) Old 04-24-2000, 09:05 PM
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Re: Electrical Buzz

It only makes the noise when the engine is on.
When I turn the key to the on position I hear the fuel pump kick on then go silent.

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post #4 of (permalink) Old 04-24-2000, 09:48 PM
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Re: Electrical Buzz

The pump seems fine then. There aren't too may electrical devices in that part or the truck you described. Here are some other ideas....

There is a back-up light / neutral safety switch located on the left of the transmission I think... perhaps that could be giving you trouble shorting out. Also the fuel pump and sending unit in the gas tank... but thats not likely to be the problem... if the sender dies it would show up with inaccurate tank readings. Have you installed any special trailer wiring harneses? Are the ABS sensors on the rear drums ok? The speedo sender? Tail-lights? Rear tailgate motor? Did you run the truck through deep water recently? Just throwing out ideas... I'd get under the truck and see if you can pinpoint the location of the sound.

Also....does the buzz sound increase when you rev the engine? Or is there a drain on the battery when you hear the buzz sound? Check the alternator if thats the case.... even thought the alternator is under the hood (you say its loudest from the back of the truck...) it could be sending electrical noise throughout the system and some otherwise good electrical component is picking it up and making the sound audiable.

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post #5 of (permalink) Old 04-25-2000, 08:17 AM
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Re: Electrical Buzz

Well if it's not the Fuel Pump, probably time to put the brake on, chock the wheels, and slide under to find it. If it only happens when engine running, could still be a mechanical resonance from exhaust system or something.
Also, if you have push-button 4WD shift, there is that shift motor on the back of the T-case. If for some reason it's stuck, and the limit switches are telling it to run, it might buzz, I'm just guessing there. Does 4Hi and 4Lo still work? Might want to see if it is buzzing first, before shifting it, or your evidence may disappear. Tapping it with a hammer may help free it up. Just a thought.


post #6 of (permalink) Old 04-25-2000, 05:59 PM
 
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Re: Electrical Buzz

I hear a buzzing sound too! I think mine is from my muffler though, might want to check your muffler for resonance like UncleDon pointed out. Just a thought

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post #7 of (permalink) Old 04-28-2000, 02:40 AM
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Re: Electrical Buzz

Located sound... seems to be coming from gas tank. Fuel pump is fine, Bronco runs great!

post #8 of (permalink) Old 04-28-2000, 10:42 PM
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Re: Electrical Buzz

Still could be the fuel pump. Broncos use a low pressure pump in the tank. Then a high pressure on the frame rail. You have to drop the tank to replace this one.

post #9 of (permalink) Old 06-05-2000, 04:26 PM
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Re: Electrical Buzz

The ABS Sensor (tone ring) and speedometer pickup are one in the same thing on the newer broncos with ABS. I do know the ground straps connecting the body and chassis are really cheezy, and I'm gonna replace mine with some 4 gauge power wire, that has bolt-on ring terminals. My CB picks up all kinda nasty noise from my fuel pump...

1994 Ford Bronco XLT - 302cid, E4OD, 32x11.5x15 Dunlop Rover RV, Rancho RS5000
post #10 of (permalink) Old 06-05-2000, 04:29 PM
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Re: Electrical Buzz

Noisy little fuel pump, aint it?

1994 Ford Bronco XLT - 302cid, E4OD, 32x11.5x15 Dunlop Rover RV, Rancho RS5000
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