How bad is it to run out of gas under load?

Portable standby generator troubleshooting and repair questions. (Gasoline, diesel, propane, natural gas)
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In the manual it says to always disconnect load before starting or shutting down, so I'm curious what happens if the gas runs out while the generator is powering the house.
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Nothing should happen from the engine shutting down it tells you to remove the load on start up to prevent engine stalling and unvoltage/underspeed alarm once the unit is at the correct rpm/htz it's safe to apply a load
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There are a couple of things that 'could' happen, but are unlikely... Running any engine out of fuel will lean the engine out since you're adding more air and less fuel. If this is a common thing, I suppose eventually it could cause premature wear on the engine.

The other thing that was mentioned about removing load is more for making sure that appliances and electronics don't see varying voltage and frequency during the shutdown. If the unit is running rough for several seconds while it's starving for fuel, the output could vary wildly. During the re-start however, you DO need to remove the load to allow the unit to start and stabilize. Trying to start an engine with load connected to it would be like trying to start a stick shift car in gear.
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Running out of gas may cause the loss of the coil's magnetism of the generator. This happens because the appliances being powered drain the remaining magnetism of the generator when the load is suddenly stopped. The result is that without a small amount of magnetism in the coils, your portable generator will not restart.
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Surge and drops in voltage and speed will make the AVR fail. Its trying like hell to regulate, going full field current and somewhere less than that. Component stress could make them fail. If its a capacitor excited, field will collapse.

Connected equipment...resistive loads wont care much, inductive loads will cry, and SMPS loads may fry.

Best thing, dont do it. :-)
Birken Vogt
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On the other hand, I have seen loads and loads of failures of a mechanical/gas nature that caused the unit to quit while connected to load, and once the problem was fixed everything functioned normally.
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