to the time that the ecology valve 43 reaches its hard stop fully energized position with the chamber 71 at pressure pxe at its maximum volume it should be noted that all three manifolds 31 a 31 b and 33 have been refilled by the volume of fuel expelled from the ecology valve chamber 55 comparing fig2 5 it will be noted that the piston 63 has the single sidewall port 64 which sequentially communicates with housing 44 sidewall ports 50 52 and 54 thus the ecology valve 43 has a first sidewall port 50 which is closed by the piston 63 when the piston is in its lowermost fig5 extreme position a second sidewall port 52 which is closed by the piston 63 when the piston is in lowermost fig5 as well as its uppermost fig2 extreme positions and a third sidewall port 54 which is closed by the piston 63 when the piston is in its uppermost extreme position the second or middle sidewall port 52 opens during piston movement between its extreme positions to couple the variable volume chamber 55 with engine fuel lower manifolds 31 while there may be piston positions such as illustrated in fig4 where the port 64 momentarily communicates with two sidewall ports 52 and 54 for example in substantially all piston positions the piston closes at least two sidewall ports all three ports are never open simultaneously 0036 fig6 shows the.