CH Boiler problems

[RWA28]

Hopefully there's some heating engineers on here tonight!
My parents came back off holiday yesterday and we can't get the boiler to work. (been switched off for 2 weeks)

It's an oil fired boiler (not a combi) and we're just getting the lock out light coming on all the time. Here's what happened:-

Turned boiler back on on Tuesday night
Went back Wednesday and lock out light was on, I thought they'd run out of oil but tank was full. Reset the lockout button and it tried to start up then tripped the breaker in the house fuse board!!!
Tried it again and it tripped again.

So today we've fitted a new control box, new ignition transformer, new capacitor, cleaned the flame detector cell, bled the fuel through to check for air and fitted a new nozzle.

Doing all this has now stopped tripping the breaker and it fires up. The problem is it fires up then after 10 seconds or so goes to lock out again.

There doesn't seem to be much else we can change other than maybe the fuel pump?

Any help or suggestions would be greatly appreciated.

[bitwrx]

Could be the fuel pump.

[dirkgently]

If it fires for ten seconds that would suggest a flame detection problem. try changing the photo electric cell.

as an aside why have I had to log on a dozen times today?

[69 coupe]

Maybe central heating pump is seized, overheating the water in the boiler causing it to shut down.

Edited to add-
Ahh, maybe not thought you wrote 10mins not 10 seconds.

Edited by 69 coupe on Friday 6th March 18:37

[Trevelyan]

Could be the pump or one of the automatic two/three way valves which isn't working. If the water isn't circulating for some reason the water in the boiler could overheat causing the boiler to lock out ...

[RWA28]

Don't think it's anything to do with overheating water as it doesn't get that far.
Could be the photo cell as that would cause it to shut down if it thinks it isn't seeing a flame. Will try that tomorrow, I'm thinking that the pump is ok as the flame is fine when it does come on for the 10 secs or so.
Thanks for all the suggestions chaps!

[robinhood21]

Have you checked to see if the water pump is working? It could have seized after a two week shut-off.

[Ferg]

The lockout won't be tripped by anything external to the boiler so forget the circulating pump etc.

I'd suspect the oil pump since it tripped it out. It runs off the back of the motor that powers trhe fan so if it had seized (water in the oil rusting the inside of the pump slightly) it might well draw too much current. You have nothing to lose by taking the pump apart and cleaning it if you are a handy bloke.

[Silver993tt]

maybe it could be the PCB?

[dirkgently]

I'm logged in. Someone go and kick the hamsters.

Had this problem on a boiler yesterday.On inspection and after a lot of head scratching, I discovered it was a faulty fire valve.May be worth checking yours.