Gas tank backpressure 1999 Windstar.

[JoeChris]

I am getting ready to do the TSB fix, However I also have an intermittent back pressure loud noise coming from the gas tank. Will the TSB also fix this or is there another problem. The only codes are 171 &174. The fuel pump and gas cap has been replaced. All hoses appear to be intact. It happens with different levels of gas.


The only way I can discribe the noise is if you place the back of your hand on your mouth and blow hard it will similate the back pressure noise. In talking to several auto mechanics none have experienced this problem.

In addition to the above I started getting very very poor gas milage since the noise started. Less than 10 mph.

[garync1]

What kind of noise from the Gas tank are you speaking of. Never heard of this one.??? I know if you let the gas tank get real low it will hiss sometimes when you open the gas cap. Now you may have a problem with the evap emissions valve. That will cause pressure to build in the tank..

[Fbednar]

My 98 just started doing the same thing. Did you ever find out what was causing the noise from the gas cap?

Thanks

[tripletdaddy]

The evap valve is at the top of the gas tank and it could become plugged or not work properly. One check is to open your gas tank cap and see if there is an unusual amount of escaping air. It would sound like a tire loosing air real fast. Pinched hoses and lines that are part of the evap system will also cause excessive tank pressure. The charcoal canister may no longer be able to hold pressure and vent properly. The evap system can be tested with a scan tool, but you may have to have a dealer or qualified mechanic to do this according to the book. If you want to tackle this yourself, get a Haynes or Chilton manual. They spell it out better than I want to type.