I recently encountered a new sound on my 96 explorer 4x4. I started my ex to let it warm up a bit, and while I was outside brushing snow off I heard it. It sounded like I had an angry badger under the left rear corner of my explorer growling at me. From what I could make of the situation, it seemed to be coming from the gas cap area of the vehicle....possibly in the filler neck. Could this be a pressure buildup in the fuel tank?......anyone ever heard this or have a fix for me?

 

Could it be the normal noise the fuel pump makes while it's running?

 

normal sound of the fuel pump running is more of a whining. this is more of a burping/belching noise. Loud too.

 

Since you asked if it could be pressure building up in the fuel tank, I'll focus there.
1) What happens to the noise if you take the gas cap off?
2) If you run the fuel pump without running the engine, what does the noise do? I'm not sure how this is accomplished, but I expect there should be a way to run the fuel pump (a fuel pump test lead or something) that allows you to run the fuel pump without running the engine.
3) Note that, with this kind of fuel system, it is possible to hear the returned fuel returning to the tank. It wouldn't be a burp/belch, but it would sound like water pouring/dripping into a bucket.

 

I am positive that it is not the fuel pump, and that it is not the fuel returning to the tank. This sound is more like a burp.....or maybe a pig grunting. not a normal sound. I have never opened the gas cap when it was making the noise. Shut off engine, then opened gas cap. Big release of pressure.

 

I don't think the fuel tank should be building up any kind of pressure or vacuum. I don't understand the complete control algorithm, but the evaporative emissions system is supposed to keep pressure from building up, and the gas cap is supposed to allow air into the tank to prevent a vacuum from building.

 

i have a 97 explorer xlt 5.0L V8 same noise sounds like a burping i was thinking perge valve but dont want to spend the money if thats not it