"Fuelling" (by which I assume you mean "fueling") may be used as a noun (gerund) or verb:
Fueling the car was expensive. (Noun use)
The log was fueling the fire. (Verb use)
When fuelling.
Kerosene or propane
The re-fuelling crew.
Re-fuelling base for aircraft and warships.
i do not know how to use embalming in a sentence. (there is the sentence)
Removing fuel from a ship. The opposite of bunkering, which is the nautical term for fuelling a ship
So- you are asking when to use 'when' in a sentence. When you are asking how to use when in a question, you are already using when in a sentence, because a question actually is a sentence. I like to use when in a sentence whenever I like.
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