Riello 40 burner - Resistance in motor shaft

[postflop]

Hi
I am having a problem with resistance in the motor shaft of a riello 40 burner which is causing the burner to lock out and not restart after running for 30 minutes or so. I have replaced the oil pump and the motor bearings but the problem is still there. There is also a medium level warbling noise when the burner is running which is definitely coming from the motor area but doesn't seem to be the bearings.
The fan seems to move freely when the pump is detached so I'm guessing the oil pump is causing the problem. Although, as mentioned I fitted a new oil pump two days ago.
When the burner runs for 30 minutes or so and then locks out, resistance in the shaft is greater and it wont restart until the boiler/burner cools.
The oil pump is relatively hot to touch when its running. It not unbearably hot that you couldn't put your hand on it.
Any suggestions on what might be the problem would be helpful. thanks

 

[Terrywookfit]

why did you replace the pump.
Did you fit a new dog ?
Remove cover of old pump and post picture of filter and metal work.

 

[postflop]

Hi Terry
Yes fitted a new dog. The shaft of the old pump was stiff and there was a coarse feeling when rotating it. Pump was the original on the burner, 20 years old
Old pump is in the bin which was emptied this morning!

 

[Terrywookfit]

Run a litre of oil into a clear bottle and check for water in fuel.

 

[postflop]

Just carried out that check and there is no evidence of water in the oil
Took the cover off the fan and started the boiler, gave the fan a helping hand to rotate and away it went. I wonder is the motor not producing sufficient power?

 

[Terrywookfit]

It is probably the capacitor needs replacing if it works with a helping hand.

 

[postflop]

Replaced the capacitor and the burner is now working. Couldn't see the wood for the trees! Had recently replaced the capacitor but the new one must have been damaged with all the other messing about! Many thanks for all your advice Terry
The noise is still there, I described it as a warbling noise but its more like a mild grinding noise. I wonder what that could be

 

[tspark3009]

The position of the fan on the shaft has to be correct so it doesn't catch the casing