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Fuel lines


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Hello, I have a 72 Datsun 510 with l20b and noticed at the back of the car there was a fuel leak, I look under and see this. Now I’m looking for some guidance on how these lines should be connected. There is two that are not running to anything anyone know which one goes where ?


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Loosen the hose clamp and push the line into the hose farther if you can then add a second clamp and tighten both.


There should be three hard lines for the three hoses. I only see two. The one being used is obviously the fuel line.


If you have the smaller tank above the fuel tank, the hose from it is the vent line and probably that's the one on the left in the picture. The tank vent line goes to the flow guide valve. As the tank empties and there is more space above the fuel it has to draw air in. Not a good Idea to suck it dust and wet from under the car. The flow guide valve is located on the left strut tower above the steering box and should have 3 lines with hoses to it. Find the one going back under the driver's side and have someone blow into it. One of the hard lines should blow air. If under the car just follow the vent line back to identify it.


The other unknown hose is probably a return line from the original carburetor. It will go up the right side of the car beside the fuel line. The L20B had provision for a return line though this engine swap may have removed it.

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The hose your finger is on looks like it used to be connected to the hard line just to the right of it.


Where do these 3 lines go once they are in the trunk?

I will try to look at my 4DR today and see what is going on with mine.

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The vent line should go to a small vapor tank above the fuel tank.


All L20Bs had a fuel return line feature. This may have been removed and the 510 lines used which should still make use of the return but????

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