Heater will not light pilot there is 11.55" water column to heater pilot valve has gas comming from piolt orfice when I try to light it won't fire up.It will light with a red reg.but gas valve on heater won't let gas through to light burners.But when I put grey reg. back on it won't light.There is 24volts on thermostat .The serial # is 46N 70411 Series "C" its a 100,000 BTU input & 80,000 output Any help ,gas pressure specs.,or manuals would be GREATLY apperciated......P.S. I included a pitcure of valves on back of heater heater