I bought my truck with a fass 150 so I never got the manual. I think i read somewhere one of the filters should be left empty when changing. Is that b.s. ,or is there a reason for that ?

 

Never heard about leaving one empty. I was about to change my filters for my first time and fill them both, but now I'll wait to see some responses on this question.

 

No need to fill the filters first... it isn't an oil pump.

 

You risk placing contaminated fuel in the filter if you pre fill it. I always install mine dry. I also recommend doing a little research on filters. I run a Baldwin BF1212 f/w separator and a Donaldson P551313 fuel filter. Good luck.

 

You fill the water separator first so you can get a good prime on the pump. The filter is installed dry. Just a coat of diesel or clean oil on the filter seal.