So, as far as I'm concerned a 'spark' can happen when electrical wires cross and the resultant 'spark' can start a fire, or the fire is already alight and 'sparks' fly making it worse by starting more spot fires.

But...

Another meaning is that a 'spark' is created by a 'spark plug' in order to force the pistons of an engine to drive the crankshaft

This leads to...

There is no spark in this relationship, so perhaps it's going nowhere.  No, we're not looking for a fiery spark, but a small amount of very intense feeling

Spark?

I was watching God Friended Me last night and I'm sure like many others we were waiting to see that spark that would change their relationship from the friend zone, to something else.

And...

it's there, but something seems to be holding them back.

As for the word spark, well there several different meanings, one of which I am familiar with when I was young.

Being called a 'bright spark'

Depending on who used that remark, it could either mean you were clever or you were a smart ass, which I suspect the latter was the reference to me.

Then, moving on

Saying something inflammatory 'sparked' the crowd into action.  A single remark can be equated to a literal 'spark' that can ignite a reaction.

A lynching perhaps?

And what about, once upon a time, a ship's radio officer, he was called 'sparks' or 'sparkie', also a name that sometimes refers to an electrician.

I can see plenty of uses for this word in a story.