Connections at the top of the fuel tank.

[wage92]

Getting ready to put my fuel tank in and i need a refresher on what lines need to be run. The big line goes to the fill port, and there is also a smaller one that goes there. However, there are like 2 other lines that come out of the tank and im wondering which one goes where? I can get a picture later if that will help....

Edit: its a 78 k5 thats carb'd with a 31 gallon tank

 

[sweetk30]

1/4 = vent to outside or canister up front

5/16 = return of gas to tank

3/8 = fuel suction feed line to engine

 

[wage92]

okay heres the next question. Running a carb, where does the return line come from?

And what size line do i use and how do i make the connections, sorry fuel lines are something ive never done before, and the way it was when i pulled it out was all cobbed together.

 

[sweetk30]

fuel pump can be had 2 ways . return line or non return . if 1 nipple line in and 1 threaded line out its a returnless pump.

if 2 nipples and 1 threaded its return style.

hard line to tank or engine pump = correct size hose and clamps in good quality rubber hose.

 

[wage92]

fuel pump can be had 2 ways . return line or non return . if 1 nipple line in and 1 threaded line out its a returnless pump.

if 2 nipples and 1 threaded its return style.

hard line to tank or engine pump = correct size hose and clamps in good quality rubber hose.

okay, i will have to check the pump to see what style it is. Thanks for the help man.

 

[wage92]

so i have one threaded in and one nipple. So looks like i dont need to run a return. So 3/8" hardline/rubber hose. And by the way you said that the nipple line on the pump comes from the tank? and then the threaded one to the carb?

 

[sweetk30]

correct. and don't forget to cap the tanks extra 5/16 " line now since you will not be using it.

 

[wage92]

sounds good. thanks alot.

One last question. the bigger hose that goes to the fill port, and the smaller one that goes that way, can they just be rubber hose?

 

[diesel4me]

If you mean the filler neck hose to the tank,it supposed to be special fuel filler hose thats unfortunately quite costly,it can be up to 25 bucks a foot--its like the hose on a gas pump at a gas station only bigger....you could look for a used one at a salvage yard ,or ,do what I did when I put a flatbed on one truck I had,and use a radaitor hose,which isn't reccomended --the peice I used never leaked or deteriorated,but it did get hard as a rock and you would not be re-using it if it ever had to come off,it would probably have broken into bits..

The smaller 1/2" vent line hose from the tank to filler neck is "special" too,but I have gotten away with heater hose,I just used good quality neoprene hose,dont get the cheap stuff...of course if you can afford the correct factory hose thats the best way to go...

If you wanted to put a return line on your truck instead of just capping it off at the tank,there are metal fuel filters available they used on older Buicks and AMC cars that had a third "return" nipple for a 1/4" hose,in addition to the two 5/16" or 3/8" nipples for fuel supply to the carb.....it was found that having the return line helps prevent vapor lock on carbed engines back in the day,most cars with air conditioning had them..

 

[dyeager535]

it was found that having the return line helps prevent vapor lock on carbed engines back in the day,most cars with air conditioning had them..

Pretty certain that by the 80's GM was installing a return line on everything. Not that I'll ever run a carb again, but were I, I'd make certain it had a return line on it. Vapor lock is one problem that is real, and a real nightmare to deal with when it occurs. If the fittings are there, get the right pump, and run it.

 

[badmix]

I replaced my rubber sections with marine grade, suppose to be more ethanol resistant fuel line, a lil more expensive but worth it if it lasts longer.