oil furnace and boiler both going out on primary control.

Old 11-08-12, 09:15 AM
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Join Date: Nov 2012
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Question oil furnace and boiler both going out on primary control.

i am a hvac service technician. i serviced a fuel oil furnace and boiler a few weeks ago. changed filter and nozzel on both. both units will run fine all day. but sometime during the night they will both cut out on the primary control. I can shut off the fuel valves, open the filter, close it back up, open the fuel lines and start them back up and they will run fine until the next day. when i open the filter it seems like it is in a vacum. you can hear it suck air for just a second then the fuel comes out. i have done this for the past 2 days with same result. the tank is underground and is 40+ years old. HELP PLEASE!

Last edited by Jkcsho; 11-08-12 at 09:16 AM. Reason: add info
Old 11-08-12, 02:58 PM
Join Date: Nov 2011
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No strainers?Need to calculate run and lift.Put vacuum gauge on pump.Way above restriction,kinked line,check or foot valve bad.Below calculated,air leak in suction line.Push pull pumps come in handy.

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