I have a Kennedy lift pump I am moving over to an LML I just picked up. After doing the custom bracket for the pump and filters and trying to get it nice and tight up against the cab floor I realized that the pump is higher than the tank. What keeps the fuel from bleeding back on a Duramax? I don't want to get air locked in the pump being higher every time I shut it off. Does the pickup-tube have a check valve or something in it? Thanks guys.