TR6 Fuel return line

[mondoslade]

I have been working on my TR6 for the past year or so. Just getting around to running the fuel lines. I bought a new tank several years ago and it has two bungs in the top of the tank with a vent nipple. I will be using a Carter electric pump with a return line regulator to supply three Dellorto DHLA 40s. The two top bungs are different as one of them has a tube that runs to the bottom of the tank and the other is just open. Can anyone suggest which bung to use for the return line? Also curious if anyone has ran the fuel lines on the right hand side of the car. It would make it easier to plumb I think. Thanks!

 

[poolboy]

Return fuel from what ?

 

[Gliderman8]

Return fuel from what ?

Same question here. What year is your TR6? Does it have a carbon canister?

 

[mondoslade]

1973. There is a return from the regulator that will go back to the tank. Sorry I didn't make this clearer. I figure I'll try running these carbs at 3.5 psi with the excess pressure returning to the tank since I didn't want to deadhead it. I am not using a carbon cannister, or any original emissions devices. The vent will use a Alston Chassis vapor cannister to take care of fuel tank pressure relief. Thanks for taking a look at this!

 

[Andy Blackley]

On your new tank check if one of the bungs goes to the bottom of the tank, perhaps into a swirl pot; use that for the supply line and the other for the return. I think a return line even on cars without fuel injection is a good idea as it keeps relatively cooler fuel flowing through the lines to avoid vapor lock. Rover used it many years ago on the 3500 sedan for that reason.

 

[malbaby]

The one running to the bottom of the tank will be for the fuel return from an injected engine.
The top/open one for air/vapour release, and will need to run outside the car, or return to the canister in the engine bay.

 

[mondoslade]

On your new tank check if one of the bungs goes to the bottom of the tank, perhaps into a swirl pot; use that for the supply line and the other for the return. I think a return line even on cars without fuel injection is a good idea as it keeps relatively cooler fuel flowing through the lines to avoid vapor lock. Rover used it many years ago on the 3500 sedan for that reason.

Excellent! Though I think my pump is gravity fed. I might have to use one of the bottom bungs for the supply side.

 

[mondoslade]

The one running to the bottom of the tank will be for the fuel return from an injected engine.
The top/open one for air/vapour release, and will need to run outside the car, or return to the canister in the engine bay.

The line running from the bottom of the tank is a return for an injected engine. Any problem using it for the return on a carbureted engine? The return pressure will be very low.

 

[Sarastro]

The line running from the bottom of the tank is a return for an injected engine. Any problem using it for the return on a carbureted engine? The return pressure will be very low.

As I read through this thread, I was thinking the same thing. The Engineering Toolbox gives a density for gasoline of 45-49 lb/cubic foot. That means you have about 0.35 PSI at the bottom of the tank per foot of fuel. I don't think that should be a problem, as long as the regulator has reasonable range.

Returning the fuel to the top of the tank does not make this consideration go away; in fact, it makes it worse. You have even more back pressure, because you are raising the fuel to the top of the tank and the fuel level inside the tank will always be less than that.

Interesting idea, though, to use the return line.