Air Dog or FASS

[gearhead]

Yes they do work well for keeping air out of the fuel. They may give you a couple of tenths of mpg gain. The main thing is that preserves your injectors. It keeps them full of fuel with no cavitation from air. Air in a injector is like a plasma cutter to steel. The air can cut away at parts and the tip. Also air effects injection timing because air compresses and diesel doesn't. So it will retard timing slightly from air. The more air the worse it will get. Plus air messes up the atomization of the fuel being sprayed. The best thing to do is take off your lift pump and remove primary fuel filter. Then put the fass or airdog in the primary fuel filters place. Put the fuel line from output of primary right to input of fuel module. But for a application where power doesn't matter as much leave lift pump in place and just put the fass or airdog in place of primary. Make sure to put toggle switch on the fass so if you have to have the key on for some reason it is not just running for no reason. The new systems have the bypass line which really helps get the air out.I am believer in it i have used sight glasses in the fuel lines and seen before and after.