Fuel system question why 2 fuel hose to tank?

[califkid_66]

Fuel system why two hose to the tank? I’m looking at the fuel diagram and it shows the fuel pump with what looks like  one input from tank then on top of fuel pump there is a t joint on output side of pump and a hose going back to the tank and the other going to the carb my question is is there a fuel pressure regulator on the output going to the tank  cause the way I see it the way it’s hooked up you would loose your output fuel pump pressure by sending it back in the tank ? I put a temporary fuel line on my europa I have one hose in a fuel canister going to the pump and only one hose coming out of the fuel pump going directly to my downdraft carb  is this ok or am I doing something wrong I still have a little leakage in the carb maybe to much pressure cause my fuel lines aren’t plumb correctly
The diagram doesn’t make sense to me need explanation or pictures of how yours are plumbed I got two tanks

[jbcollier]

One hose is the supply to the pump.  It draws close to the bottom of the tank.  The second hose is just a return.  The second outlet on the pump has a metered orifice to allow a small amount of the pump's output to return to the tank.  This means the fuel pump always has fresh, cool fuel.  This is important as the exhaust manifold is right below the carb and fuel vaporization is an issue.

Are you using the stock mechanical pump or an electric fuel pump?

[califkid_66]

It’s mechanical but the pump seems to have only one input and one output  and ai saw pumps that have one input two outputs if I got one input and one output should I put a t joint at the output end of the pump to be able to send one hose back to tank and one to carb but then would I not loose my pressure to my carb

[califkid_66]

Ok according to the diagram I am connecting my fuel line the wrong way I connected a hose from the fuel pump directly to the carb  according to the diagram I should have a three way t connection on the output side and send one hose to the carb and the other to return in the tank
My question is  is this correct?

[jbcollier]

Yes, but the return has to have a metered orifice in it.  You only want a small amount returning to the tank.

[califkid_66]

I understand what you mean it’s sort of like an injection system fuel rail pressure regulator but I looked  in the lotus service parts list and there’s nothing except a t connection could it be that there’s enough pressure in the pump to fill the carb and the excess goes back to the tank ?

[BobW]

From the tee, the fuel supply line (the straight-through line) goes to the carb. The line coming off the tee's metered orifice is the fuel return line. That orifice is quite small, about the diameter of a small needle. I've never seen a good explanation for this line, though it appears to me its purpose is to bleed off excess fuel pressure from the carb.

For what it's worth, the replacement aluminum fuel tank I had installed last year arrived with only one fuel line connection. I queried the supplier, who said the fuel return line was unnecessary. That seems to be the case, although I notice the smell of raw gasoline in the garage after I've parked the car. If you don't have the original metal tee, you could consider blocking the return line at the tank.

[califkid_66]

I was running the engine without a return and when the car ran a bit I was running rich and started having a leak inside the carb I thought it was because of to much pressure but then I put the t the car ran great for a moment and dried out then I blocked the hose with a bolt and made a small hole to relieve the pressure car ran but started leaking again inside so I guess it’s the float cause I changed the needle valve the problem is I can’t find info on adjusting it so I’m gonna have to wing it

[califkid_66]

Finally found my lotus fuel pressure regulator it’s funny how in the parts Manuel you can’t see detail like these that make all the difference in your system