fuel filter question

[sethsbseries]

I changed it yesterday and it has 2 lines in and 1 line to engine my question is the 2 lines in what are they for? The bigger line I couldn't blow through at all the small line coming in I could. What's the big an Little's incoming lines??? Note: this is on an 06 3.0

 

[cvar]

On the double side is a high-pressure inlet line from pump and the return line for surplus fuel back to the tank. On the single side is fuel line to engine.

 

[RonD]

Yes, ^^^

Bigger line is from the fuel pump and fuel pump has a check valve(back flow preventer) so no you shouldn't be able to blow thru it.
Smaller line returns fuel to the tank so is open at both ends, you could blow thru this one, fuel filter would have a valve inside for this line to prevent over 70psi pressure from building up.

 

[sethsbseries]

Thanks guys it was original with 122k miles on it, black fuel came out but wasn't clogged.