Are there many -tion words that sound like 'vision'?

Usually -tion words, such as motion, education, and lotion, end with a -shn sound. But equation ends with a sound rhyming with vision.

Are there many more? What might some of them be? And if the pronunciation of equation is a rarity for words ending in -tion, why did that pronunciation for it arise? I'm asking this since I am not a native English speaker and discovered this exception accidentally.

I've read through all of the words beginning with a through c in WS2's very useful list of -tion words, and so far I've found that the vast majority of the words in the -tion family carry a sh sound at the beginning of the final syllable.

The main exceptions to that pattern are some words ending in -stion (bastion, combustion, congestion, counterquestion, countersuggestion, etc.) or in -ntion (attention, contention, convention, circumvention, etc.), which instead carry (in typical U.S. English) a ch sound at the beginning of the final syllable.

There is also a red herring in the form of cation, which is of course not a -tion ending at all, but a cat[a]- prefix attached to the root word ion.

Most significantly to the point of the OP's original question, none of the a through c words in WS2's list carries the sound zh at the beginning of the final syllable.

[One hour later...] I finished reading through all of the -tion entries at MoreWords.com, and the only one that—in my generic U.S. English pronunciation—has a zh sound at the beginning of its final syllable is equation. I should have taken Peter Shor's word (in a comment above) for it.

I did come across the variant spelling kation to go with cation, and I encountered one interesting exception to the -ntion exception that I noted earlier: To my ear, at least, dissention carries a sh sound (and not a ch sound) at the beginning of its final syllable; but dissention is a bit weird anyway because it is a variant of the more common spelling dissension.

Anyway, I am fairly confident that the answer to the question "How many -tion words are there whose last syllable sounds like the last syllable in vision?" is one.

This seems to have been a change in the last hundred years or so. Walker's Pronouncing Dictionary from 1828, has "shun" and not "zhun", as does Webster's 1892 High School Dictionary (available via Google books).

It's possible both pronunciations were around in the 19th century, but clearly the /-ʃən/ pronunciation was considered "correct".

Since this appears to be a unique sound change that happened quite recently, it may be impossible to find a good explanation for why it happened.

For more evidence that this was a recent sound change, in his 1850 poem Misunderstandings, Lewis Carroll rhymes equation with observation and nation. The middle verse is as follows:

Now to commence my argument,
I shall premise an observation,
On which the greatest kings have leant
When striving to subdue a nation,
And e’en the wretch who pays no rent
By it can solve a hard equation.

(Note the unusual stress on the second syllable of the verb premise, which agrees with Walker's 1828 dictionary pronunciation for the verb: /priːˈmaɪz/.)