Rear fuel lines

[Zero_cool]

What is the middle fuel line on the sending unit for?
The P/O just stuck a bolt in the end of the line.
I only have 2 lines going to the engine, is the 3rd just a breather?
If so should i take the bolt out and just let it dangle off the frame?

 

[AceHigh]

These have 4 lines. Fuel supply, return, siphon line to the bottom of the tank and vent to the fill line. The siphon line goes off to the side and is blocked off.

 

[Zero_cool]

I only have 3 lines. Forgot to mention its a m1028.

 

[AceHigh]

Most of the aftermarket senders have 3. The military wanted the siphon line added.

 

[notsosanestan]

you can get a regular gas engine sending unit and it will have the 4 lines