Oil burner with sludgy mucky oil

apw99

Hi all - I had a look at a friends oil burner tonight, its about 20years old but in very good nick. The heating would not fire up at all. Plenty of oil in the tank, last filled 4 weeks ago and has been in constant use. It burns MGO (gas oil). The injector and cowl were very black and the injector had wet oily deposits. Sparker working fine. The light sensor was dirty so I cleaned that up. No joy with firing. Checked the fuel-pump for an air-lock and no flow of oil (???) so i looked at the bowl filter which looked kind of black anyway. Turned off the oil and took out the filter and it was a mass of black guey sludge. Cleaned it all out and turned on the flow into a clean container and could see black sludgy deposits coming through. Flowed it for a while and cleaned up the filter and housing. Ran through the fuel pipe by disconnecting at the pump, reconnected and bled the pump. Could not get a fire so i changed the injector nozzle with a used one I had from before and it fired up and ran fine. Could not see the color of the smoke in the dark. I don't expect this will last for long as the fuel is definitely dirty.
So - the last fill of fuel could have been dirty but just took a few weeks to flow through???
Any other ideas why the fuel would get so mucky?

Any help appreciated - you guys got me out of a few holes before!! Thx,
APW

DoneDL

it might not be the fuel, most likely its poor sevicing, not dipping the tank for water and not cleaning the filter anually which leads to crap in the fuel line.

apw99

If there was some water in the oil would it actually cause sooty black deposits to appear in the oil? I would have imagined it would just float on top?
Thx.

DoneDL

very much the opposite, and the pump will suck in the contaminated oil.

apw99

Thats true - I've forgotton all my childhood war films with the sinking ships and burning oil!! Thanks, Appreciated!
APW;)