1. IN A FLUID METERING DEVICE, A METER HOUSING COMPRISING A CYLINDRICAL BODY AND A CLOSURE MEMBER COVERING ONE END OF SAID BODY, SAID BODY DEFINING AN AXIALLY EXTENDING METERING CHAMBER AND A DOWNWARDLY EXTENDING BORE COMMUNICABLE WITH THE LOWER END OF SAID CHAMBER, SAID CLOSURE MEMBER BEING THREADABLY SECURED TO SAID BODY AND HAVING AN AXIALLY EXTENDING BORE COMMUNICABLE WITH SAID CHAMBER, SAID CLOSURE MEMBER HAVING A TRANSVERSELY EXTENDING PASSAGEWAY COMMUNICATING FLUID TO SAID LAST MENTIONED BORE, FITTING MEANS COMMUNICATING SAID PASSAGE WITH A FLUID SOURCE, A CYLINDRICAL FLUID OUTLET TUBE MOUNTED COAXIALLY OF SAID CHAMBER AND HAVING ITS LOWER END RIGIDLY SECURED WITHIN SAID FIRST MENTIONED BORE, STOP MEANS ON SAID TUBE, SAID TUBE HAVING AN AXIALLY EXTENDING OUTLET PASSAGE AND A TRANSVERSELY EXTENDING PORT COMMUNICATING SAID PASSAGE WITH SAID METERING CHAMBER, A RESILIENT DEFORMABLE SEALING RETAINER SLIDABLY DISPOSED WITHIN SAID CHAMBER BETWEEN THE TOP OF SAID OUTLET TUBE AND A PORTION OF SAID CLOSURE MEMBER, DEFINING SAID CENTRAL BORE IN SAID CLOSURE MEMBER, SAID RETAINER BEING SLIDABLE WITHIN SAID CHAMBER TO AND FROM A POSITION SEALING SAID BORE IN SAID CLOSURE MEMBER, SAID RETAINER HAVING A DOWNWARDLY EXTENDING PERIPHERAL FLANGE SECTION YIELDABLY ENGAGEABLE WITH THE PERIPHERY OF SAID METERING CHAMBER, A PISTON ASSEMBLY SLIDABLY ALONG SAID TUBE AND COMPRISING A RESILIENT DEFORMABLE SEALING MEMBER AND A HOLLOW CYLINDRICAL SPACER, SAID SEALING MEMBER BEING IN SEALING ENGAGEMENT WITH SAID TUBE AND SAID PERIPHERY OF SAID METERING CHAMBER AND INCLUDING AN UPWARDLY EXTENDING SHOULDER PORTION THAT IS ENGAGEABLE WITH SAID STOP MEANS ON SAID TUBE, AND SPRING MEANS RESILIENT URGING SAID PISTON ASSEMBLY UPWARD WITHIN SAID CHAMBER TOWARD SAID RETAINER.