I have a Teledyne Laars EPM 175,000 BTU heater and it started up just fine. I shut it off to save on fuel cost and went to turn it back on it wouldn't ignite. So went through the steps again and re lit the gas pilot and came on just fine but it will not innit unless I jumper it on the coil and the th side of the gas valve. I change out the therostat a couple of years ago with a compuerized thermostat with a blinking light. The light is no longer blinking. The Heater use a pilot generator to produce the the current that is neccessary to ignite the burners. I replaced the pressure swith. I put a jumper from the coil to the black lead of the pressure switch and a jumper to the th on the valve to the white wire of the pressure switch and it fires every time. Any sugeestions what could cause it to not to fire.