2012 loud buzzing from secondary fuel filter.

Steve Mutter · October 2, 2014

I have a 2012 6.7 that is buzzing from the secondary filter. The line with the green clip from the secondary fuel filter is buzzing and if you put your hand on it you can feel it vibrating as well. I have changed the filters, tested the inlet restriction and found it around 3 inches. I have a know good pump so I installed it and I still get the buzz/vibrating line. This truck does have a bigger fuel tank in it with some kind of tuner. The odd thing is if you shut the truck off and cycled the key on and off several times to prime the fuel system you can then restart the truck and let it idle and it doesn't make the noise. But as soon as you rev the engine up past 3000 RPM the buzzing/vibrating starts up again. The other odd thing is when you have the truck running and it's making the noise from the line you can go under the truck and cracked the water separator a little bit and the noise goes away. Has anyone out there come across something that seems similar, not quite sure what to think about this one. Any opinions would be helpful.

cbriggs · October 2, 2014

Only time I have seen that line buzz is when air is entering fuel system. We chased one for a while, and ended up finding the fitting on the top of the sending unit was cracked.

lmorris · October 2, 2014

Disconnect the fuel inlet at the pump and run the truck off another fuel source. Could be the pick-up in the tank too.

Steve Mutter · October 2, 2014

Thanks for the tips! I found the supply tube cracked on the sending unit. Installed a new sending unit and road tested, all good!

cbriggs · October 7, 2014

Good to hear!

leavnon3rd · October 7, 2014

ive had a few do this if i didnt prime the primary filter and just key on a few times before starting, i prime the bowl everytime now.

Also seen a a dozen or so do then when the service man did a service and over tightened the bowl, or jacked up the oring and it wasnt tight enough.

cbriggs · October 31, 2014

Steve what was the mileage on the one you had? I just had another one (easy diag now) and both of the ones I've seen were around 100k. If it was a manufacturing defect you would think it would show up long before then. I noticed on the one I replaced yesterday that the flex line from the frame to the tank was very stiff, and I think the line is putting pressure on the fitting and cracking it from vibration on rough roads.