98 Chev 1500 5.7 fuel evap code

I have a fuel evap help code that first only came on after it rained but for the last 4 months it is always on. It is not the fuel cap. over a year ago I replaced the fuel pump and filter. There are no leaks under the truck and the mileage is as poor as it always has been so no change there. What is usually the problem and is it easy to fix? Could it be the sensor or is it the fuel fill neck?

I have a fuel evap help code that first only came on after it rained but for the last 4 months it is always on. It is not the fuel cap. over a year ago I replaced the fuel pump and filter. There are no leaks under the truck and the mileage is as poor as it always has been so no change there. What is usually the problem and is it easy to fix? Could it be the sensor or is it the fuel fill neck?

the fill neck is possible as it does rust out...if so you can use metal mender if not to bad...fill neck is 200.oo plus...

if you drop down the fill neck you will see if its bad...also smell for vapors...with cap on...it only takes a pin hole..

Take it to a shop that has a smoke machine and this is the only way to find an evap leak.