Gmc Headscratcher

[Bryce]

Vehicle is a 2012 crew cab long box 6.0 liter with 60k miles. Problem has been happening for about a year. Back into the garage and it sounds like a fan is running under the box. Only things in that area are the muffler and the fuel tank.  Rear end is behind the sound. Loud. Like when you walk in front of a vehicle in a parking lot and the auto fan kicks in. Can hear it now from almost 50 feet away. Only time I have ever heard it is in my garage when pulling in after the trip home. Never in a hotel lot that may have have a similar trip. If it's a overheating isssue, I should have heard it other times. I probably cool down the truck as I get close to home better than staying on the road. If I let it run to see what happens,  the battery will be dead in less than 45 minutes. Piling in the dogs and cruising neighborhood  for 5-10 minutes has usually helped but headed out on my second trip.

[Macgyver55]

Hard to say without hearing it but my first thought would be maybe the ABS pump motor might be stuck on? Only thing is they are usually up under the driver seat area of the frame.

Edited April 9, 2016 by Macgyver55

[rustysetter]

I know the fuel pump used to be in the gas tank,  I'm guessing they still are, is it possible that is malfunctioning in some way to keep pumping? Just a guess there's not much in that area with an electric motor. I have a 2012 extended cab with a 6.0 and haven't experienced anything similiar.

[Macgyver55]

Yes, they are still in the tank, but I can't say I have heard any as loud as you describe, and it would sound the same while it is running. 

[Bryce]

Manager of our truck fleet is leaning towards fuel pump stuck wide open. Left the battery unhooked last night in hopes of resetting a relay. No such luck or maybe actually lucky in that a mechanic can now witness the ailment. Strange that it would only act up in my garage. 

[Jeremy airjer W]

If you suspect a fuel pump than you can pull the fuel pump relay in the underhood fuseblock and see if the noise goes away?

 

[Bryce]

It was the fuel pump making the noise. Did it once more time since and pulling the fuse shut it off. Fuse was extremely hot but I didn't put much thought into it. Monday it pretty well died on me. Just enough left to limp it 30 miles to the shop. Was strange that it ran smooth after cooling off while switching some gear into a spare truck. Ended up being an issue in the fuse block and they are replacing the entire block right now.

[Jeremy airjer W]

[Bryce]

Company is a good customer and they understand our needs for these trucks so they put in a new fuel pump as well under the warranty. Gave it a good workout the past two days. Almost 500 miles and a lot of heavy trailering. 

Edited May 20, 2016 by Bryce