79 dual tank fuel lines

[mybigtruck]

I have 79 with dual tanks and I need to know how to hook up the lines. I am hoping for a definitive answer to my question.

I have been doing quite a bit of reading and am just getting confused.
Here is how I think things work. The valve input connections are: 2 each, Fuel Supply and Return. The two outputs connect to the engine mounted pump Supply and Return. Now for the big question. There are three lines leading up toward the pump, a 3/8ths, a 5/16ths, and a 1/4 line. I am sure the 3/8ths line is the fuel supply line. But I am not sure about the remaining two. Some things I read say "the 5/16ths line is vent and the 1/4 line is return. Some say the other way around. I think 5/16 vent and 1/4 return is correct but I would like to hear from some one who really knows these dual tank systems. Can any one help?
THX

[ray_mcavoy]

1/4" return and 5/16" vent is correct.

Since you have a system with a return line, your tank selector valve should be a 6-port unit. It should have three 3/8" ports (a left tank inlet, a right tank inlet, and an outlet to the fuel pump). It should also have three 1/4" ports (a left tank return, a right tank return, and a return connection from the fuel pump). The 5/16" tank vent lines do not run through the selector valve.

[mybigtruck]

Thanks for the quick reply. That's the way I thought It was but I ran across some info that was confusing. Now I can finish my hookup.