1972 C3500 402 4spd with 5/16" fuel lines?

[jumpsoffrock]

'72 California truck, SPID says it all.

My fuel gauge sender is bad, and everywhere on the internet says I should have three lines, Rockauto only has 3-lind fuel pumps for my truck, and every sender for my "V8" truck is said to be 3/8". The internet even tells my my sender should not have a flare nut on it, and that it simply connects with a piece of hose. Nope not my truck......what the heck is going on???


What have I found on this truck? The sender is 5/16", if I hold a 5/16" open ended wrench over the line it fits around it perfectly. The line bolts to the truck frame line, no rubber hose connection.

My fuel pump only has 2 lines, there don't appear to be any stray lines that look like they were hooked up and then abandoned at any time.



I really don't want to order the wrong part, but my truck is some kind of anomaly, can someone confirm if they have 5/16" factory lines in a big block truck? Thank you.

[Steeveedee]

A 1T will not have the vapor canister, I think. So two lines on the fuel pump. Do you have AC? As for the fuel line, my '70 has 3/8".

[Ol Blue K20]

My 72 has 3/8" also. No EEC two line fuel pump. I believe the 5/16" is 6 cyl....

[jumpsoffrock]

Can one of you guys "measure" the actual fuel line, or do like I did and put an open ended wrench? Will a 5/16" wrench fit over the line?

Maybe I'm measuring wrong or something....

[57taskforce]

I’ve never seen a 67-72 with anything but hose at the connection points between the tank, tank hardline that goes down the tank and thru the floor then to the frame line and frame line to fuel pump. Could you post pictures of your setup? Your truck should only have 1 line supplying fuel to the pump and no return, as well as no EEC.

[jumpsoffrock]

Sorry for the poor pic, but here it is.

[pjmoreland]

That's what my sender and fuel line look like, and my fuel line is 5/16". My truck came with a 307 originally.

[1970cstblazer]

This is NOS GM 6428082 listed as fitting all conventional cab trucks except 327-402 and EEC. This has a 5/16" line and the fittings..

[jumpsoffrock]

I fooled myself and everyone here with my laziness.

I got under the truck and checked the lines to find 1) the original factory style hose clamp hanging and a modern hose clamp used instead. (this made me think someone had been here before)
2)....oh yeah and the factory untampered fuel line that runs along the frame rail? 3/8"


I am lazy, I am a fool. Ok ok.... but....
So somebody actually went through the effort of switching out senders to a 6cyl line size sender, and also adding the flare nut style instead of hose clamping?

I'm gonna guess junkyard special.

Either way I'm ordering a proper 3/8" sender, and get a new stretch of hard line from the sender to below the cab.



Thank you for any thoughts everyone.

[Steeveedee]

Given the time involved, all kinds of crazy things can happen to a vehicle. Don't feel too badly about it.