Loud buzzing noise from the fuel tank area in hot weather

[stioc]

I've noticed this on multiple occasions that when it's hot out there's a loud buzzing (even with the car shut off and keys in your hands) noise coming from the driver's side rear wheel area. My guess is that it's the fuel pump that runs until it cools down to help extend its life? I've only heard it when it's 90F+ outside.

[Rebelord]

Hmm. I dont think that is intended. In tank electric fuel pumps should stay cool enough running just when the truck is running.

What you can do to test if it is the fuel pump. Is go ahead and remove the inspection cover for it. Take it for a drive when it is hot outside. Then when you shut off the truck and hear the humming. Open the hatch and feel if the fuel pump is still running. If so, maybe the heat over time may have degraded some insulation somewhere causing a ground to keep the pump running even when the truck is shut off.

 

Long shot, but worth a try at least.

[Towncivilian]

Change your fuel filter if you haven't done so in the past two years.

[stioc]

Hmm. The fuel filter has less than 1k miles on it- and even if it was old why would it make the fuel pump run after the ignition has been shut off? Is there anything else in that area that could be running/buzzing?

 

I'll check for electrical shorts too but I think it's unlikely.

Edited May 6, 2013 by stioc

[Alkorahil]

That is caused by a wornout/stuck check valve in the rear ventilation line going to the fuel tank when the tank is trying to equilize pressure. The diaphram in the valve is vibrating as pressure changes in the system when the system equilizes pressure.

Nothing major, more annoying than anything else.

Eventually if the valve totally fails it may cause a CEL code like P0456 'minor evaporate system leak'

[stioc]

Thanks Rob! I found a lengthy discussion here and the last post pretty much said what you just described.

 

http://forums.nicoclub.com/humming-sound-from-rear-when-car-is-off-t554548.html

 

Where is the check valve, got a diagram handy or reference to the FSM section? I need to order a few things so I might add this to the list too.

[Alkorahil]

PM me your email address and I can send you the diagram.

 

17370-0W010 VALVE ASM

28.95.

 

 

 

As a follow up, it will most likely do this when you are about 1/8 a tank or less, and in warmer temps.

You can also make it stop immediately by opening the fuel cap if its driving you crazy.