fuel pump or gas cap problem?

[acb384]

today my 99 Avalon would not start, turned over but never fired. It read about 1/4 tank of fuel but I tried putting a little gas in anyway. Got a sucking sound when I opened the tank and splashed a gallon of gas in and it fired right up. I didn't think much of the sucking sound but then the car would not start again the next time I went to start it today. I tired the gas cap and got the whoosh again so I just left it a little lose, now its working fine. I thought a new gas cap was the problem like maybe it was not venting air in (i know they are not supposed to let gas vapor out) and too much vacuum pressure built up. The people at the auto parts place said the fuel pump was likely dying but I dont know if that makes sense.

[Jack Deth]

my 99 doesn't make a sucking sound when i take the gas cap off. it doesn't sound like the fuel pump, but more like something in the evaporative emission control system. i don't know exactly how it's hooked up. in the camry forum there are links posted to online shop manuals, the avalon should be similar in layout. that's where i would start. good luck.

[Jigg007]

In my 1996 Avalon, when I go from a full tank of gas to under a 1/5 tank, removing the gas cap causes a whooshing noise, presumably air being sucked in from a negative pressure inside the tank, as it doesn't smell like gas when this occurs. However, I've never had any issues prohibiting a startup.

Speculation, but I believe there is a pressure line that goes from from the fuel tank to the charcoal canister or other evap modules- modules that relief the pressure but contain the gasoline vapors. It is possible that maybe a line is damaged, prohibiting the relief of pressure. I apologize, but I do not have much knowledge in this area.