Just browsing through the WWW and found the following on a site about oil fired burners

"If you have problems with fuel leaking into the combustion chamber during the off cycle and rumbling when it starts you can add a solenoid to stop this problem. When the pump pressure drops below 80 PSI. a valve should stop the flow of oil, if it doesn't oil will continue to flow if the tank is above the burner."

I think that my bruner does this when it turns on. Also my tank is located above the burner. Has anybody ever come across this scenario? Me thinks that if the oil does leak into the combustion chamber it's an awful waste of oil???