Ideal Classic FF240 - Firing up but not staying on longer than 60 seconds

Ok thanks I'll give the upright bleed and the pump a check and if not it'll be engineer time
When your boiler lights, the pilot is established and it sends a message to the PCB to open the main burner solonoid (Flame rectification or Ionisation is the technical name) but what is happening is when the main burner lights, there is a restriction in the Pilot assembly and the flame drops out as the main burner uses the gas, hence the constant on off, it is just the sequence constantly repeating itself, quite a common fault on your boiler, but well worth repairing, they are great very reliable boilers
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Update on this

After checking the pump I ended up calling a plumber in to have a look. He went round and did a similar check to the pump and diagnosed that the boiler was blocked due to sludge in the system and I needed a powerflush. Essentially the pump wasnt able to move the water through so the water was sticking in the boiler and boiling off which would then tell the boiler to shut down as it had reached temperature

I was a bit skeptical at first about the powerflush and concerned my old gravity fed system would spring a leak somewhere. The powerflush was done yesterday and happy to report this has solved the issue. The boiler no longer shuts off before time, all the rads are hot all the way up and HW works correctly as well. I ended up having a new Grundfos UPS3 pump fitted (£113 Screwfix) and new valves either side (2 x £8 from Screwfix, power flush guy wanted to charge me £50 per valve!)

Grundfos have an app called Grundfos Replace whereby you put in your pump part number into the app and it then reccommends the pump you need to replace it with otherwise I wouldnt really have known what to buy. Again the power flush guy wanted to charge me £230 to supply the pump but I ended up getting it myself for £113

All in it was:

£90 fault diagnosis
£113 Grundfos UPS3
£16 Gate valves
£485 Powerflush (4.5hrs work for 2 x guys)
= £704

A bit steep and not ideal for this time of year but I'm happy its working and the Ideal Classic lives on to fight another day....for now
As a follow up to this, the new pump is very quiet. Its made a big difference in noise levels when the pump kicks in. The boiler seems much quieter as well

The only thing I have noticed is, it sounds like theres still air in the system as I get a kind of intermittent bubble rushing sound through the pipes near the pump area under the stairs. I am going to let it settle for a couple of days and bleed the rads to see if I can chase it out
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Spend another £14 and put a bottle of Inhibitor in the system if you haven't already, or you'll be back to square one again in a couple of years time.
Bled all the rads of air today, working from furthest away to closest to the boiler downstairs and repeating the process again upstairs. All of the downstairs rads were fine, no air at all, however 2 of the upstairs ones closest to the boiler (boiler is downstairs) had a fair amount of air inside. I thought this might be the case as I've been hearing the water pumping into the rad and literally dropping in from the top so assumed there was some sort of air cavity in there

I'd read about hydrogen in old systems so tried my luck lighting the gas coming out. Thankfully no burn and it was just oxygen!

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