Europa 24 struggling to ignite.

[Franky1977]

Hi, this is my first post on this site. I have a 5(?) year old Europa 24 combi, which I now know is a cheap and nasty little number. I have had to change various parts over the 2 years I have known it including the diverter valve, PCB (last year), gas valve harness, and fan. All of these parts were diagnosed and not just change and see.
At the moment it is struggling to ignite on both CH and DHW. It looks like a general sequence problem. For the most part it will start up as per normal. Pump runs, fan runs, igniter operates, gas valve opens, and ignites. But it usually only ignites for a split second before the gas valve is shut off. I have checked continuity of the APS with the fan running, and it was fine. There is zero resistance over the OH thermostat terminals (this was even temporarily bridged) so I don't think it's that. All flow switches and low water switch work fine with a good contact. Every 10 or so attempts the boiler fires up and when it does it runs smoothly with a healthy blue flame. Can't afford a new 1 yet, any ideas?

 

[methaneman75]

check the condition of the flame sensing electrode and if in doubt give it a rub with some steel wool and check the gap between it and the burner is around the thickness of a pound coin

 

[Franky1977]

Thanks Methaneman, I actually deduced it could be the flame det elctrode/igniter so these were both replaced a few days a go and gap set, to no avail. The burner ignites well, but only for a split second. On some tries, the sequence operates but not to the igniter stage, before locking out. It's starting to look like an intermittent problem.
When the boiler runs, it can do so for up to half an hour before shutting itself off. The problem is that after shutting off, it will try to restart a short time later. Thats when the firing problem occurs. Oddly enough, when the boiler shuts off after this half hour (sometimes 5 mins) period, it looks normal, no red light. This appears to be normal function of the room stat. But to eliminate a room stat problem, I disconnected it and bridged the terminals at the PCB a while ago so the boiler at the moment is always calling for heat,. and operated by the power switch. I know this ain't a great way of doing things but i'm trying to rule out one thing at a time.
My next idea would be the APS, I'm sure this is the last signal before the gas valve opens. Can they be temperomental? Please don't be the gas valve.

 

[methaneman75]

its pretty hard to determine what is wrong with it without standing in front of it. Sounds like there is possibly more than one fault with it.
As you say it could be the APS ,sometimes these get stuck in the no prove position or the diaphragm part bursts,you could use a multimeter on this with the boiler switched off and suck through the impulse pipes and check using resistance setting on meter to see if getting continuity or OL when making switch.
Also , what is the potentiometer/boiler stat on the boiler set to, it may just be getting satisfied when you say boiler just looks normal

 

[Franky1977]

Cheers mate. I know it can be twice the task when you're not actually there to see the symptoms. I'll give the APS imp pipe a charge and check accordingly. It's a Honeywell part so I thought it might outlive every other piece on this travesty of a boiler. At the moment I can actually see the five pound notes radiating from my electric fire and into the atmosphere.