walshie Posted January 4, 2016 Report Share Posted January 4, 2016 My lad has an external oil-fired boiler at his place. It works OK, but when it is set so the stat calls for heat, the boiler flue fan starts as it should, the boiler fires, but goes off again a few seconds later, then fires again for a few more seconds - all the time the flue fan is running. This on-off-on-off thing goes on for a couple of minutes then it fires and stays lit for as long as it's required. Any idea where to start looking? Ta. Quote Link to comment Share on other sites More sharing options...
Medic1281 Posted January 4, 2016 Report Share Posted January 4, 2016 Air in the fuel line? Small leak somewhere? Quote Link to comment Share on other sites More sharing options...
fenboy Posted January 4, 2016 Report Share Posted January 4, 2016 I am no expert , but I had a similar issue a few years back and it was a sensor that is suppose to see the flame that was dirty . Has it had a service recently ? Quote Link to comment Share on other sites More sharing options...
aga man Posted January 4, 2016 Report Share Posted January 4, 2016 I am no expert , but I had a similar issue a few years back and it was a sensor that is suppose to see the flame that was dirty . Has it had a service recently ? Yep this is certainly the first thing to try, clean the photocell [magic eye] wipe with a soft cloth. Quote Link to comment Share on other sites More sharing options...
walshie Posted January 4, 2016 Author Report Share Posted January 4, 2016 Yes it was serviced this Summer and obviously we haven't used it since then to notice. Odd thing it it works fine after a few minutes. Quote Link to comment Share on other sites More sharing options...
oowee Posted January 4, 2016 Report Share Posted January 4, 2016 I am no expert , but I had a similar issue a few years back and it was a sensor that is suppose to see the flame that was dirty . Has it had a service recently ? +1 had the same thing. Its now changed every year when they service the boiler. Not expensive. Quote Link to comment Share on other sites More sharing options...
walshie Posted January 4, 2016 Author Report Share Posted January 4, 2016 Magic eye. Thanks. I'll have a look. Quote Link to comment Share on other sites More sharing options...
bullet1747 Posted January 5, 2016 Report Share Posted January 5, 2016 Magic eye. Thanks. I'll have a look. Had this a few times on mine Quote Link to comment Share on other sites More sharing options...
wisdom Posted January 5, 2016 Report Share Posted January 5, 2016 Bit of a daft question due to all this rain could the fuel be contaminated with water.Does he have a water trap in the fuel line? Quote Link to comment Share on other sites More sharing options...
walshie Posted January 5, 2016 Author Report Share Posted January 5, 2016 Bit of a daft question due to all this rain could the fuel be contaminated with water.Does he have a water trap in the fuel line? Yes and there's no water in it. Quote Link to comment Share on other sites More sharing options...
kent Posted January 5, 2016 Report Share Posted January 5, 2016 My lad has an external oil-fired boiler at his place. It works OK, but when it is set so the stat calls for heat, the boiler flue fan starts as it should, the boiler fires, but goes off again a few seconds later, then fires again for a few more seconds - all the time the flue fan is running. This on-off-on-off thing goes on for a couple of minutes then it fires and stays lit for as long as it's required. Any idea where to start looking? Ta. Fuel filter first check. Could also be the fire cut off sensor that cuts the fuel at a certain temperature in case of fire they fairly regular fail If you don't know how to check these call an engineer as it could be a few other things Quote Link to comment Share on other sites More sharing options...
Banger123 Posted January 5, 2016 Report Share Posted January 5, 2016 It's either not firing properly either due to lack of fuel at injector or spark not lighting it. the photo cell could be breaking down. Call an engineer is the best bet Quote Link to comment Share on other sites More sharing options...
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