grammar - Is 'could V' always present or future?

When there's no other verb which indicates the tense in a sentence like

I could eat it.

, not like

I did all I could.

, then does the could-phrase always have present or future tense?

In other words, when the "could+V" is the only verb in a sentence, can this have any meaning related to some past event?

(except the negative form or could+have+pp form or any other special(?) verbs such as "hear","smell")

Answer

When used as a modal verb, then, yes, "could" by itself always refers to present or future possibility.

I could answer this question.

If you want to use this in the past, use "could have"

I could have answered this question.

I'm not sure what part of speech "could" is in, "He did all he could", but as it refers to past events, I see it as an ellipsis for something like:

He did all he could have done.