Merlin Boiler lockout problem

Hi,
Can anyone help please. I have a ten year old series 2000 Merlin Boiler, model 80/100. The lockout light comes on shortly after start up but the boiler can usually be restarted and then continues to run ok. The problem has been ongoing for about 3 years and two engineers have been unable to rectify the problem despite replacing many parts.
Specifically what happens at startup is as follows:
Relay clicks and oil pump starts up
After about 10 secs. relay clicks and ignition occurs
After a few secs. flame extinguishes but a few secs, later relay clicks and re-ignition occurs.
This "hunting" occurs a couple of times but eventually ignition fails and lockout light comes on.
Unless I can get the problem resolved I am going to have to go for a replacement boiler as constant unsuccessful visits by engineers is costing me.
Hope someone out there can offer advice.
Regards,
Swagman

Is it balanced or conventional (chimney) flue? If BF it could be recirculated fumes getting into burner air supply through snorkel. There shouldn't be any faulty components, the burner is doing it's job by shutting down if combustion is not ideal.

Try using a competent engineer, this dosn't sound like an impossible fault to fix to me I'm amazed that you have had so many so called engineers in front of it who have not been able to sort it it soes sound like a flue or recirc problem to me, just a thought though are the baffles correctly installed in the boiler as if even one is the wrongf way round or they are in the wrong order, the flue gasses cant flow through the boiler properly which will cause the symptoms you describe!

Boilerman2 said:

Try using a competent engineer, this dosn't sound like an impossible fault to fix to me I'm amazed that you have had so many so called engineers in front of it who have not been able to sort it it soes sound like a flue or recirc problem to me, just a thought though are the baffles correctly installed in the boiler as if even one is the wrongf way round or they are in the wrong order, the flue gasses cant flow through the boiler properly which will cause the symptoms you describe!

Click to expand...

Many thanks Boilerman2
As I said to Tibbet, engineers have tested for flue or recirc problems (is this vitiation ?) but until recently the problem has been intermittent and never occurs when they are present. I should add that the last guy, in desperation I think, permanently disconnected the air inflow pipe so that air for the burner is obtained directly from the space around the boiler. This seems not to have made any difference except that the boiler noise is more noticeable.
Swagman

If snorkel removed, air setting will need adjusting and combustion re-checked.