77 Coupe DeVille Fuel line replacement

[Andy R]

...the fuel lines on my car started leaking and need to be replaced. does anybody know the correct sizes for the vapor and return lines? the supply line i believe is 3/8 inch...thanks

[Misfit]

Correct. The return should be 5/16" Fuel Injection or Carbureted?

Fins

[Andy R]

it's carburated...how about the vapor line?

[Misfit]

The vapor line runs from the charcoal canister back to the tank itself, and is 5/16".

The actuation line for the canister is 3/8" and is connected to either the intake, or the rear lower plate of the carb.

Fins

[ANDY R]

thanks a lot for your help! this'll be my little weekend project...

i did a little research online and just saw that they are sellling replacment return lines at 1/4 inch (main at 3/8 and vapor at 5/16). are you sure about the 5/16 on the return line? i guess the return line hooks up to the carburator, right?

thanks, andy   

[TJ Hopland]

The sizes are correct.    The vapor line goes to the charcoal canister.  The return and supply lines go to the fuel pump which is on the Left front of the engine.    While you are thinking about it dont forget the same 3 lines back by the tank.  There is a little over 1' of each rubber hose between the tank and the hard lines that go along the frame to the front.  There are steel lines from the center to edge of the tank.  Its a little tight but you can get the clamps off with a needle nose pliers.  Its above the rear axle so it can be a little awkward to get at depending on how you raise the car.  Its worth it though.  I have had a few failures causing at the least a leak if not sitting dead on the side of the road and replacing a perfectly good fuel pump.   

[ANDY R]

thanks.

I just did the the whole lenght of supply line (all rubber fuel hose, since i had to do it on the cheap) and noticed that somebody must have done part of the return line already. From the canister to the passenger door it's the Original 1/4 steel line and from there on the steel line was replaced with 5/16 rubber back to the tank. Should I replace the 5/16 rubber hose with the correct size 1/4 hose or just leave it the way it is???

The vapor line looks pretty good, so i'll just leave that alone for now.

thanks for the help!

[TJ Hopland]

I have had trouble with that length of hose on the supply (suction) side.  I have bought a few cars that were that way.  I dont know if its the more chances for kinking or the length under suction tends to collapse.  I replace the steel line with steel brake line.  Its readily available and not very expensive.  The 3/8 can be tricky to bend but its not that bad unless you are going for an exact factory look.  You can buy threaded couplings to connect sections.  For the ends you can just cut the pre made end off and slide a hose on with a clamp or two.  You can just use nylon wire ties to hold it in or try to get it under the factory clamps.    Under the drivers side door and just before the back wheel seem to be the most common places to have a rust problem on all american cars from the 70's and 80's. 

[ANDY R]

yeah, since it's done already i guess i just see how it works out for now and keep an eye on it. if i run into trouble i guess it would be a good idea to replace sections with steel brake like as you had mentioned. how about the return line issue that i mentioned above? thanks.... 

[TJ Hopland]

I dont think the line size is going to hurt as far as the flow.  The concern is how well the larger hose will connect to the hard line.  You dont want any leaks. 

[ANDY R]

...it's been on there for a while and it seems to be tight with no leaks....i'll keep an eye on it. i appreciate all your time and input...thanks, andy