A diesel pile hammer housing is seated upon a pile and a ram moves alternately up and down within the housing, striking an anvil and driving the pile. The ram and the housing cooperate to define a power chamber and a separate scavenging chamber that are interconnected for gases to flow from the power chamber to the scavenging chamber. During the diesel operating cycle, upward movement of the ram creates a sub- atmospheric pressure in the scavenging chamber and gases are drawn from the power chamber into the scavenging chamber. During starting operation, the ram is elevated by a generally cylindrical push rod that fits through a circular guide bushing in the housing to contact the ram within the scavenging chamber. An intermediate portion of the push rod is deformed from its generally cylindrical shape by removal of a segment thereof to form a flat surface along one side of the rod. This deformed portion of the rod and the circular guide bushing define a vent between the scavenging chamber and the atmosphere, as the ram is elevated by the push rod. Thus, atmospheric pressure is maintained in the scavenging chamber, making it easier to lift the ram and to maintain a reed valve in a closed position between the power chamber and the scavenging chamber and thereby retain fresh air in the power chamber. The upper cylindrical end of the push rod forms a seal with the guide bushing during the diesel operating cycle.
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