Practical Classics (UK)

Floating fine, or in floods?


QHow can I check the float level in my Peugeot 205's carburetto­r ? I think it's flooding, or at any rate, overfillin­g at idle.

Dan Smith, Brecon

Ed says

ALook up the correct float level (and method of adjustment) in a manual. Don't adjust use guesswork - this tends to solve one problem while causing another. Carry out other simple checks. Since the problem is only at idle, is the float needle valve loose in the body of the carburetto­r? If so, fuel leaks past it, bypassing the valve. Is the fuel pump delivering too-high a pressure? It should be between 3-5psi. Buy a fuel pressure gauge (for carburetto­r cars) and connect it to the hose feeding the carburetto­r. Start the engine on the fuel remaining in the carb and measure the pressure both at idle and high revs. If too high, the float needle valve is forced open. Place thicker gaskets between the pump and engine to reduce delivery pressure. Does the engine shake excessivel­y when idling (not just when on the point of stalling)? This throws the float around, opening the valve when it should be closed. Attend to the causes – blocked jet; ignition timing; broken HT lead; wrong valve clearances or valve timing.

Adjusting the float level is done by bending the tangs of the float, or on other models by adding a thicker copper sealing washer under the valve body. Unless the carb has a sight glass in the float chamber, or the facility to force a plastic tube in place of a plug near the float chamber base (photo) you can never really know what's going on with the engine running – so instead you have to be doubly sure that everything else is in order.

 ?? ?? Force a tube in place of a jet: fuel level in tube is same as that in float chamber.
Force a tube in place of a jet: fuel level in tube is same as that in float chamber.

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