Potterton Profile 80eL Pilot Light

[tim-spam]

There appears to be an intermittent problem with my 2 year old Potterton Profile 80eL boiler, in that the pilot light has failed to light twice recently, and sometimes seems to take a long time to light. Normally, it lights after one or two sparks, but recently, can take up to a minute of sparking to light.
When the system calls for heat, the fan starts as normal, followed by a click, and then the ignition spark starts clicking, but the pilot light does not ignite. There is a slight smell of gas from the flue, so it appears that there is at least some gas being supplied to the pilot. The spark does not appear to be particularly strong, and it tends to vary in strength, but there is definitely a spark. When the pilot does light, it appears to be the right shape and size as far as I can tell in the brief period until the main burner ignites.
From looking at the fault-finding guide, it appears that the most likely culprits are:
1) Solenoid GV1 not working consistently.
2) Electronic control failing.
Another possibility could be contamination on the pilot light jet causing the gas to be (sometimes?) diverted away from the spark (boiler serviced around 9 months ago).
Before getting someone in, I would appreciate some advice from people on this forum about what is the most likely cause of the problem, given the symptoms and type of boiler.

 

[Agile]

Firstly I would question the boilers age. As far as I know the Profiles were discontinued several years ago.

The most likely cause in your case is that the boiler has not been properly serviced and the pilot jet just needs checking and cleaning. CORGI job of course!

Tony

 

[geoff@cetltd]

If you measure the voltage to the gas valve solenoid, that would tell you whether it's the pcb or not, wouldn't it

 

[millview]

My 60e recently suffered a similar problem. The fault was with the metal pole electrode that delivers the spark. This is fitted into a vertical ceramic sleeve, which had slipped slightly in its mounting - the gap between both elctrodes was thus too big. Simply sliding this back and carefully retightening the fixing nut cured the problem.

 

[tim-spam]

Thanks for the replies.
Unfortunately this fault is intermittent, so I am reluctant to call anyone in - for example, when I checked last night, it was working perfectly. The pilot ignited several times with the first spark, and the pilot light itself was, as far as I could see, exactly as shown in the picture in the Potterton manual, both in terms of size and shape. I suspect that it may be temperature related - both times it's failed to light have been in the early morning when first trying to light. The second time it failed (yesterday morning), I switched the system off and on again 3 times, and then it lit after sparking for around a minute. Then, for the rest of the day (and this morning), it has behaved perfectly.
I was thinking that it may be a dodgy connection to the pilot solenoid valve, although yesterday morning, I could smell gas coming from the flue outlet, which would seem to suggest that there was gas coming from the pilot jet. It may be a weak spark, although there was definitely a spark, and I would expect even a faint spark to light the pilot. So, I guess I just have to wait for it to fail again and then go through the faultfinding procedure. I really would like to have a pretty good idea of what the fault is before calling anyone in - if I had called someone yesterday, they would have witnessed a boiler working perfectly and charged me for the privilege.
I will check the central metal pole on the electrode though - I assume it should be visible through the spy hole - although the gap looks to be around 3mm, which is supposed to be OK.