Fuel-air mixture was generated by a Solex 4A1 carburetor. It is of the double-register type, as with the previous model W114. That means each of the two sets of mixing systems feeds three cylinders and each of these two sets is composed of a first relatively small mixing system for idling and a second, larger mixing system for higher load and higher speeds. At idle and up to about one-third load only the smaller tube of each set is mechanically operated by the accelerator pedal, while the second tube of each set is enabled by a vacuum cell only at high load and high engine speed. All four (2 x 2) tubes are supplied with fuel by a central float chamber. The engine is equipped with gasoline feed line and gasoline return line (which usually was more typical for fuel injection engines) achieving a cooling effect which protects from vapor locks, that would cause starting problems in hot weather.
