Question about S2 fuel lines

[jjbunn]

My car has a single fuel line from the tank to the mechanical fuel pump, and a single line from the pump to the Weber carb. The return inlet on the tank is blocked off.

If I were to re-use the return inlet, would I add a metal T to the pump-carb line, and connect a line from the T to the return?

When I was idling the car for an extended period of time yesterday, I noticed that every now and again the fuel tank would "clonk" as if its sides were flexing! I attributed this noise to the release of pressure, and this got me wondering about its cause.

Since the pump is sucking fuel out of the tank, there needs to be a way for air to get into the tank, right? If my tank is too well sealed, will it cause the tank to flex as the vacuum in it builds up, and cause the noises I heard? Will it cause fuel starvation? Is this alleviated by the return line (which is not there on my car)?

[rascott]

my (i think) stock setup had a tee after the fuel pump.
the tee had an orfice to restrict flow back to the tank......
i used a fuel filter from an old jeep(carbureted cj?) that has a bleed port.
i'll find a filter # and add to this post.......
just a thought. perhaps the fuel cap should vent? my car has no evap. emission, my tank doesn't seem to care.
richard

wix33040

[jbcollier]

The tank needs to be vented.  Early Europas used a vented cap.  Make sure your cap is vented and the vent is not plugged.  If you have a later Europa with emission controls, the tank is vented through the evaporative system.  Often this is removed and plugged "to improve performance".  Make sure, even if it has been removed, that the tank is still able to vent.

That should sort you tank "clunking" problem.

The fuel pump return circuit is to maintain a supply of cool fuel to help reduce the chances of fuel percolating in the float bowl -- something to which all none cross-flow engines are susceptible.  The proper Renault fuel pump had a metered bypass built into the pump.  If your's doesn't have one then you can fit one in the line from the pump to the carb.  Use a BRASS tee and solder up one outlet for the return.  Drill a very small hole, 1/64 is plenty.

Europas have a lot of engine fires.  Always use quality fuel fittings, clamps and hoses.  Route lines carefully, supporting them where required.  If you do not carry a fire extinguisher, you should!

John

[jjbunn]

The tank needs to be vented.  Early Europas used a vented cap.  Make sure your cap is vented and the vent is not plugged.  If you have a later Europa with emission controls, the tank is vented through the evaporative system.  Often this is removed and plugged "to improve performance".  Make sure, even if it has been removed, that the tank is still able to vent.

That should sort you tank "clunking" problem.

The fuel pump return circuit is to maintain a supply of cool fuel to help reduce the chances of fuel percolating in the float bowl -- something to which all none cross-flow engines are susceptible.  The proper Renault fuel pump had a metered bypass built into the pump.  If your's doesn't have one then you can fit one in the line from the pump to the carb.  Use a BRASS tee and solder up one outlet for the return.  Drill a very small hole, 1/64 is plenty.

Europas have a lot of engine fires.  Always use quality fuel fittings, clamps and hoses.  Route lines carefully, supporting them where required.  If you do not carry a fire extinguisher, you should!

John

Thanks, John - very useful! I replaced my old fuel tank cap with a new one, which seals quite well (evidently!). So I bet that's the problem. Do you think I should drill a small diameter hole in the cap?

[jbcollier]

if you can do it without having it visible. Other get a vented cap, there cheap.