Boiler goes out but pilot light stays on

[Grizza]

Myson Orion 75Si. 15yr old
New pump fitted last month so circulation seems fine. Recently though boiler lights up, runs a short while then goes out leaving pilot light on and a feint clicking as if a spark trying to ignite pilot is going. It also sounds like the extractor fan is still running.
I know the extractor fan may be on it's way out as in the past I've used WD40 to keep the spindle free running. When it got clogged in the past the pilot light wouldn't even start.
Could it be the fan just isn't running fast enough even though it's running?
Any other ideas please?

 

[gas4you]

Sounds like a lack of circulation to me. Are the radiators getting warm? has it worked properly since the new pump has been fitted?

 

[nickso]

could also be the dreaded fan timer board if its the model that has one.....some do some dont.

they are a nightmare. i once fitted 4 in a row until i got one that worked.....new out of the box

dont remember that affecting the pilot though. these also have a strange aps setup which can go wrong and the main pcb's arent that great either.

 

[Grizza]

It's working again at the minute. I started to open the cover with the pilot light still on and the bolier lit up - perhaps not that bright an idea with hindsight , but it's working - perhaps inflow of air ? I did think that some of the radiators weren't getting that warm to start with so I turned up the pump setting to 3 and they're all nicely hot now. I've bled the key radiator that seems to get the air trap.

Have to wait for it to go wrong again...

 

[gas4you]

If boiler fires up with cover off it usually points to dirty or blocked fan venturi, aps or damaged aps sensor tubes.

 

[nickso]

or maybe a damaged spark lead if your having pilot probs.