With the gas tank, if you just fill it and flop the lid down I noticed they dont seal that great. THen push it down alittle bit more and it makes a good seal. Also check the rubber oring and see if it is not defective. If yours still doesn't build up a vacuum then you either have a bad gas tank or a pin hole in the lines..
The springs are sensitive. I had some that broke fast or just unhooked. After that they lasted good.