RIELLO OIL BURNER - ONLY STARTS WITH KNOCK TO MOTOR !?

Hello everyone

My oil boiler (1995) has a Riello G5 burner, it would not start this morning and was on lock-out when I got up etc.

The motor does not start but there is a kind of buzzing (might be a solenoid?) anyway, before it went to lock-out again I gave the motor a sharp (but light) knock with a spanner and it started and ran no problem for 6 hours.

I have tried the same trick 3 times now - knock with spanner - and each time it gets it to start and it then runs fine.

It can't be much so has anyone any ideas PLEASE?

Do motors in Riello Burners have brushes? I was thinking that the spanner knock is making the (worn out ) brushes make contact??

All Suggestions Welcomed
Many Thanks
Grahal

It's most likely tight spot on pump or capacitor.

Gunge in the pump. Strip and clean!

No brushes in motor, just a solid rotor and wound stator coils. As Nixt suggested, look at the capacitor, and preferably measure it. They get damaged by voltage spikes over the years which results in gradual lowering of its value.

At present it maybe the pump, though checking the capacitor is easier to do first, rather than removing the pump.