My shop has the schrader hook ups for my fuel lines so I can do an injection service and I want to do it. One of the techs said on my 5.3 theres some kind of return line that all the injector cleaner will just go back into the tank because of. Is this true and if so what do I do? Block it off?

 

block it off or run low pressure. it will only return if the regulator opens and allows it to.

 

Well it has to be hooked up to an air line.

 

if its the pressure canister type there should be a regulator on it, just screw the end onto the schrader, hook your air up to it and turn the pressure down to 30ish psi, just enough for it to run but not very much more so you lessen the chance to bypass the regulator.