I have added a new Fass system and had it put on by the dealer(I am lazy) and I noticed that the injector pump only had the fueling line and not the return(defueling) line put in and they put a plug in...Will this hurt my injection pump?

please email me at xcomandos@aol.com and put reply on this page so others can learn

 

That doesn't sound right. Not sure what year your truck is, but mine is a 2001 and according to the holy service manual:

"...approximately 70 percent of the fuel entering the pump is returned to the fuel tank through the overflow valve and the fuel return line...".

maybe it is different on other generations...lets see what others say...