Hummmmmmmm sound??

[dogrider]

Well i got the truck home. And love it so far. Its like a caddy compaired to my 7.3. I was giving it a good cleaning today and key in start position to listen to the radio and I could hear a hummm sound under the hood. It was on or hummed the whole time I cleaned. I couldn't figure out where it was coming from. Any ideas???????? Will i hurt anything leaving it in start without engine running. Anyway it sure is a nice truck. It was made 01-08 is it a job1 or job2. Thanks Chris

[rlpzzz]

Maybe the vacuum pump for the four wheel drive? I had a broken vacuum line once that made a hum when the ignition was in the on position.

[IA Farmer]

I could be wrong but it might be the fuel pump.

[dogrider]

Thats what I thought it was, but does it stay on. I check it more tomorrow.

[Dim Sum]

Sounds like the vacuum pump. Its on the driver's side up next to the firewall I think.

BTW, good looking FX4!

[rlpzzz]

Fuel pump shuts off after about 30 seconds, look under the hood drivers side in between fire wall and battery, I'm fairly confident it's the vacuum pump.

[AW794]

Was the key in the run position or the accessory position? If its in the run position the fuel pump and vacuum pump will run. It shouldnt hurt anything, maybe just leave it in the accessory position the next time. It wont make noise and your radio will have power.

[eberlestock]

Thanks guys. My new company truck does the same thing. It doesnt stop humming when its running and my auto lock hubs dont work either. Vacumm pump sounds right.

[rum4]

on my 2010 it was a vacuum pump

[dogrider]

Thats right its coming from the drivers side behind battery. Ok then if I put it in the aux position the dinger drives me crazy. Can you take out the dinger. I used to take the out of 90 model chevys, but wasn't sure because these are to techie and thought it my have to stay in. That also brings me to another question............

It has auto and lock on the hubs. They are in auto now. Please explain how they work. If I turn switch in 4x4 will it been in or do I have to get out and look them in. Thanks Chris