Spartan74

I'm totally new to the LS engine world so this is a basic question. I acquired a salvage yard 2002 Yukon 5.3 that I'll use in my F100 restomod. I also got the factory Yukon fuel line tubing that came from the tank. I'm unsure of which tube on the fuel rail is the supply line that feeds the fuel and which one is the return. One size tube is larger than the other.. which is which ? I would expect the smaller one that's going to the pressure regulator is the supply line..A basic question for you veteran LS jocks.. Thanks for your response..

gagliano7

The larger line is the feed and the smaller one is the return.

G Atsma

Look at it this way; fuel comes in, some gets used, the rest goes back. Which line SHOULD be larger? HINT- The gas tank is being emptied while this is happening...