Oli boiler - photocell not seeing flame?

[Tel9]

Is anyone able to help me with this problem.
I have an old Heating World wall mounted oil boiler which is regularly serviced and rarely used.
It was working fine then was switched off for a week.
It now ignites, runs half heartedly (it used to roar) then locks out after about 10 seconds.
Ive replaced the photocell, control box and oil pump.
Ive checked the oil pressure which runs as 10 bar and have tried to adjust the air flow.
Ive looked inside the combustion chamber. the nozzle looks fine and there does not appear to be any wear on the electrodes.
Ive also removed the baffles and cleaned out the chamber
If i take the photocell out and expose it to a lamp the burner keeps going even though its still not a roaring flame as it was before this problem occured. I can see the oil buring through the photocell mounting.
The inline filters are clean and clear.
The only unusual thing is some black oil in the Tiger Loop bowl but i'm not sure where this contamination comes from.
As it was working fine before this problem it has to be something benign but i can trace it.
Any suggestions where to look next please.

 

[Terrywookfit]

It would have been cheaper to get you regular service bloke in.

A new nozzle and check your oil for water would help.

 

[dcawkwell]

Start off with new nozzle as it sounds as if it isn't burning correctly.

Tiger loop should be clear oil so there is a problem with the fuel.
dirt from tank being drawn in if you have an old steel tank?

 

[Tel9]

Thank you for the quick response.
I guess the nozzle is about the only thing left even though it looked in good shape.
Its definately not burning properly so i assume the photocell is not seeing enough light and its locking the control box out.

 

[dcawkwell]

Thank you for the quick response.
I guess the nozzle is about the only thing left even though it looked in good shape.
Its definately not burning properly so i assume the photocell is not seeing enough light and its locking the control box out.

Yes if the photocell doesn't see the burn it will lock the burner out in about 10 seconds.
Sequence of events is usually fan starts, check photocell for dark, spark ignition firing, open fuel solenoid, check for burn, ignition spark off..

 

[Tel9]

I've finally got the boiler sorted out and running well.
Just to conclude this thread in case anyone was following it or needs information in the future.
The poor burn a being caused by a small family of eight snails that had crawled into the air intake and had settled right up against the air adjustment baffle plate thereby severely restricting air flow.
Early on I had checked the intake pipe itself which seemed clear and i had not seen this blockage until i completely removed the burner.
The snails were removed, everything reconnected and the boiler runs really well.
I will be installing a open mesh over the air intake to prevent this in future!

 

[Boilerman2]

Another example of how a little knowledge can be a dangerous thing!! that was one very expensive lesson in DIY £150 worth of un-necessary parts!!
it would have cost about £80 for a pro to sort that one out!!