Hi guys. I am having a problem with this one. Burner consistently locks out after 12 - 20 minutes of use. Have given the unit a standard service, changed nozzle, cleaned all oil filters including pump and baffles etc. Have checked oil line for leaks. I had a spare control box and photocell in van which didn't work either. I am thinking it may be pump / solenoid based (specifically the coil). Is there a way of checking this. Any thoughts would be gratefully received. ta