Sterling Burner Problem

[AaronC]

So I got called to a burner where they had the problem of it won't fire in the morning and they have to hit the button on the control box for it to fire. I have changed the pump and the box, but its still doing the same thing? I have checked the oil filter and its spotless, also I serviced it a few months ago and checked the nozzle and its still as good as new. The oil supply is fine too

Anyone any idea what else it could be?

 

[Best]

Could be a few things. First of all, I assume, as you changed oil pump then the solenoid is new, so it could be motor capacitor or photocell. Also burner could be set wrong which won't start on cold start in morning. Check spark is healthy & that motor seems strong, with no bearing noise.

 

[AaronC]

Yep, new solenoid with pump. When we did fire it, there was no bearing noise, sounded healthy enough. In what way would the burner be set wrong that it won't start on a cold morning?

 

[kimbo]

It could be overaired, you have to make an allowance for summer settings and winter settings, warm air has less oxygen content than cold air hence if it is a cold morning and the boiler is setup right on the borderline it could have too much oxygen.
I agree with best on everything else, it could also be air in the oil line, check there are no weeping joints. My bet would probably be with the capacitor as Best says

 

[Best]

As Kimbo says, too much air to the oil mixture will prevent it igniting or burning correctly on start up, & can lock out. Very common when we get cold mornings. Usually caused by air setting too high, but obviously if oil pump pressure is too low or nozzle partly blocked, same happens.
Capacitors seem to be a common fault on Sterlings. Try listening carefully to burner motor start by switching burner on a lot of times. If it sounds sluggish on the split second start any one time, then change the capacitor.

 

[AaronC]

Cheers folks

 

[Best]

Sorry, I had said solenoid in last post but meant change capacitor! Have edited it now.

 

[smitty]

Try an ebi transformer had bother with few of these intermedent

 

[WHPES]

If the motor turns OK and it only trips when it comes on in the morning, sounds like you are getting air in the fuel line.

Without seeing it, if I were guessing I would suspect the following scenario - fuel supply is lower than the boiler and there is a slight leak in the supply pipework allowing air in, causing the oil to fall back down the pipe to its natural level due to gravity. The air coming in is only gradual so it's only when the boiler has not been operating for a significant length of time that the oil has run far enough back down the supply pipe that the fuel does not reach the pump before the controller times out.

Rectification - firstly the usual culprit for this is a wheel head fire valve as these are prone to leaking as they age. Use a Rothenberger type pressure test pump on the line (at the tank end) and when you pressure it up with oil (6 bar), the leak will become obvious.