keston celsius 25

[Viper Gas]

Hello All,
was called to a keston celsius 25 to check escape of gas.
I found gas escaping from a broken fan seal as the boiler was running.
The gasket was replaced but now the boiler will not fire up.
tried it many times until and eventually it fired up?
it was running sweetly but then i decided to turn the boiler off so i could connect manometer to check burner pressure and now it wont fire up again???!

does any one have any clues here????
blocked condensate?
block exhaust flue?
all air purged from gas pipe work?
theres a little test point which says VENT on the gas valve, if this gets blocked, say with detection fluid will this impede operation of gas valve?

cheers

D368

 

[lame plumber]

if its a vent and its full of detection fluid that might not be helpful, get your air duster out

 

[Plumb Ugly]

I had this problem with a worcester greenstar after I'd serviced it, turrned out I'd knocked a little grey rubber bung off a vent point on the gas valve! Stuck it back on fired up no problem! Could be the same valve

 

[lame plumber]

my normal trick on baxi 105/80s is to pull off the flame sensor lead slighlty so it stays in the rubber sleeve but not on the metal contact, but I seem to do it so often I can spot the problem quickly now!!