Ever since I've owned my truck (1 1/2 years), there has been a high pitched whistle or whine from the fuel tank area while the truck is running. It used to be just the rear tank. About a year ago, I replaced both the front and rear pumps with new pumps. Since then both tanks make this whistle sound while running.

I'm wondering if this sound is somehow related to tank venting. The sound doesn't come from the filler opening but from the tank. Looking through the LMC catalog, I see the vent valve component. Can these fail? Could these somehow be the source of the noise? TIA

 

Could just be the pumps? Possibly the one was replaced with an aftermarket and it whines, then you replaced both and now they both whine.

That high pitch "whine" noise was a lot more noticable back in the early days of fuel injection but I think with technology they have isolated the noise better.

 

Both are ford pumps. I guess it could be the pumps but I keep thinking it sounds like an air leak.

 

Mine does it too. Its the fuel pumps.