S1 Fuel Line Plumbing

[My S1]

Thought I would go through the fuel system and replace the sender and lines and add an in-line filter but I was aghast to see this wild two step playing out between 1/4" and 1/8" fuel lines.  Checking vintage magazine article pictures and the shop manual I found that my situation is exactly as it left the factory.  Is this a brilliant example of masterful hydraulic engineering prowess that I am too feeble to grasp?  Why do the inside diameters fluctuate so?  Would I be a fool to simply run 1/4" lines throughout and possibly reduce the pressures or increase volume?

[jbcollier]

The plastic lines are not 1/8.  They are thin wall so more like 3/16".  Regardless, it worked.  However, they are all VERY old and should be replaced without a doubt or delay.  Running the 1/4" hose is a fine idea.  Use ethanol-happy fuel line.  Be careful how it is routed and support it where needed.

I would also plumb back in the plugged off third line.  It's a metered feed back to the tank to keep the fuel circulating and cool as the engine compartment can get very hot.

[My S1]

Interesting, thanks. 

There is a "T" piece on the line from the pump to the carb presently.  Not sure if it is original.  Is one return outlet better than the other for the function mentioned?

[My S1]

Just noticed in the shop manual that the "T" is original.  We must have picked up a less than original fuel pump sometime in the past 56 years.

[jbcollier]

Some Renault pumps have the third port, some don't.