So im new here and am not sure of where to post atm but ill post here for now. so i have a 1999 gmc jimmy it is 4dr 4x4. So pretty much i got ahead of myself and didnt mark the lines when i removed them off the fuel pump. the fuel pump has 3 ports. port furthest to the passanger side labelled with an F furthest to the driver side is R. then the middle isnt labelled. pas side has the largest diameter so i cant mix that one up. but the other 2 im kinda confused on now. The R would stand for return right? So the line coming from the frame that would go to that port would be the one run to the front of the tank and to the rear of the frame near the filler neck. that line has a "t " connector in it. and the last line connects in the middle and follows the frame just like the supply but by passes the filter and connects shortly after. sorry if all this is jiberish sounding but idk how else to say it. but the bottom line is im mixed up on the smallest two lines. thanks for any help

 

Put 12v to the pump and see which tube has gas coming out :P

 

Thank but i think i got the supply figured out and thats about. i need help with the other 2 thanks

 

3 different sizes, ya can't mess 'em up

3/8" is pressure to the injectors.
5/16" is return from the regulator.
1/4" is fuel vapor to the purge canister.