WEAK EXPLOSIONS
Regular but weak explosions may be due to too rich or too poor a mixture, or to the escape of compression. Cranking the engine twice will produce a compression stroke in each of the four cylinders, and if there is a leak, the ease with which the piston in which it occurs may be pulled over dead center will show its presence. A little soapy water around the spark plug, relief cock, or other opening into the combustion space will show the escape of compression in the formation of bubbles. A hiss inside of the cylinder indicates a leaky piston ring, or that the openings of the rings are in line, and when this sound is sharp and clear, the presence of a broken ring. An additional proof of this is the undue heating of the crank case. If the compression is correct, the carburetor may be readjusted to improve the quality of the mixture. A poor mixture may be due to the partial clogging of the spray nozzle or its passages, and a rich mixture to the choking of the air inlet by dirt or dust, this being especially liable to occur when the part is oily.