Riello RDB2.2 warm start issues

[JHolland]

I have a Riello RDB2.2 in a Bosch Worcester Greenstar Heatslave II. The burner won't fire when its warm, it used to fire during the winter one time and then wouldn't restart until it had cooled again. I have changed the motor capacitor because that was leaking and also the main jet and electrodes which were a few years old. When it did run it had a good 8bar of oil pressure. Has anyone come across this issue before?

 

[ShaunCorbs]

Motor bearings ? Oil pump eg when warm things expand so locks / stiffen up