Low oil shut off

A few years back I bought a tiny, very used and abused 1 axle trailer off a retiring paving contractor. It has a 3 cylinder diesel - I think it's an Onan - powered 7.5 kw generator with a hand cranked exendable 20 foot tower, four halogen lights, and folding anti-tip outriggers. Honestly, I've neglected it; but it's run great, makes plenty of power for my needs, and nearly lights up my whole junk yard. It's motor faces the rear, and has an electric fan with shutters that open when it starts to run hot. Today, while using the generator without lights it shut down and wouldn't restart. After lunch I looked it over I found out that when I put the key in the preheat position the low oil light and a buzzer came on. I checked the oil and needed to add two quarts. After I added the oil it started right up and has run fine since. Obviously it has a sensor of some kind and I am glad it does - but how did it know it was low on oil and to shut down? Does it work off oil pressure? How did it shut down? I have to turn the key off and pull a cable to stop fuel flow whenever I want to shut it down.

 

Hello Nut and Bolt King!

If it has a low-oil sensor, it most likely works off of oil pressure. I imagine, on a diesel, it would have a pressure sending unit that grounds when the oil pressure gets low enough. On the fuel system, there may be a solenoid with power to it, and the ground running to the pressure switch. When the switch grounds, the solenoid activates, turning off the fuel. This is about the only thing I can imagine for a diesel cut-off system, since there is no ignition to kill. I have not seen one of these engines though, so this is speculation. I can't think of any other practical way though.