Pumppu toimii, mutta rengas pysyy tyhjänä.

A word-for-word breakdown is:

• pumppu = pump
• toimii = works / functions
• mutta = but
• rengas = tire (or ring, depending on context; here it means tire)
• pysyy = stays / remains
• tyhjänä = empty, in the sense of remaining in an empty state

So the structure is very close to:

• The pump works, but the tire stays empty
• more naturally in English: The pump works, but the tire remains flat

Toimii is the normal Finnish verb for works / functions / operates when talking about a machine, device, system, or method.

So:

• Pumppu toimii = The pump works
• Auto toimii hyvin = The car works well
• Tämä ratkaisu toimii = This solution works

English uses work in this way too, so this is a very direct match.

By contrast:

• on toimiva means something more like is functional / is one that works
• tekee työtä literally means does work / is working in the sense of labor, not machine function

So for a pump, toimii is exactly the natural choice.

Toimii is the 3rd person singular present tense of toimia (to work, to function).

The basic pattern is:

• minä toimin = I work / function
• sinä toimit = you work / function
• hän/se toimii = he/she/it works
• me toimimme = we work
• te toimitte = you (plural) work
• he/ne toimivat = they work

Here the subject is pumppu, which is singular, so you use toimii.

In Finnish, two independent clauses joined by mutta (but) are normally separated by a comma.

So:

• Pumppu toimii, mutta rengas pysyy tyhjänä.

This is standard Finnish punctuation, just like English often writes:

• The pump works, but the tire stays flat.

Each side could stand as its own sentence:

• Pumppu toimii.
• Rengas pysyy tyhjänä.

That is why the comma appears.

Because rengas is the subject of the second clause.

In:

• rengas pysyy tyhjänä

the tire is the thing that stays/remains in a certain state. Subjects are usually in the nominative form, and the nominative here is rengas.

Compare:

• Rengas on tyhjä. = The tire is empty/flat.
• Rengas pysyy tyhjänä. = The tire stays empty/flat.

You would use other cases in other roles:

• renkaan could be genitive/accusative in other contexts
• rengasta could be partitive in other contexts

But here, plain rengas is correct because it is the subject.

Pysyä means to stay, to remain, to keep being in a state.

So:

• Rengas on tyhjä = The tire is flat
• Rengas pysyy tyhjänä = The tire stays flat / remains flat

The verb pysyy adds the idea that even though the pump works, the situation does not change. The tire continues to be empty.

That contrast is important:

• the pump is functioning
• but the tire still does not fill up

So pysyy is more informative than just on.

Because after pysyä in this kind of sentence, Finnish often uses the essive case to express the state in which something remains.

• tyhjä = empty (basic form)
• tyhjänä = as empty / in an empty state

So:

• rengas pysyy tyhjänä literally means something like the tire remains as empty

This sounds unusual in English if translated too literally, but it is normal Finnish grammar.

A similar pattern appears with other adjectives:

• Ovi pysyy kiinni. = The door stays closed.
• Hän pysyi rauhallisena. = He/She remained calm.
• Maito pysyy kylmänä. = The milk stays cold.

So tyhjänä is not random: it marks the continuing state after pysyy.

Tyhjänä is in the essive case.

The essive often answers the question in what state? as what?

For adjectives, it is commonly formed with -na / -nä, depending on vowel harmony.

Here:

• basic form: tyhjä
• essive form: tyhjänä

Because the word has front vowels (ä), the ending is -nä, not -na.

Some more examples:

• valmis → valmiina = ready
• hiljainen → hiljaisena = quiet
• kaunis → kauniina = beautiful
• tyhjä → tyhjänä = empty

So the sentence uses the essive to describe the tire’s continuing state.

Literally, tyhjä means empty. But with a tire, empty naturally means without air, so in English the most natural translation is often flat.

So:

• rengas on tyhjä can mean the tire is empty literally
• but idiomatically, it often means the tire is flat

Finnish is focusing on the tire being empty of air, while English usually focuses on the result: flat.

Both are good ways to understand the sentence.

Yes, but the meaning changes slightly.

• Rengas on tyhjä. = The tire is flat.
• Rengas pysyy tyhjänä. = The tire stays flat / remains flat.

The version with on just describes the state.

The version with pysyy emphasizes that the state continues, often despite an attempt to change it. In this sentence, that matters because the first clause says:

• Pumppu toimii = The pump works

So the full meaning is something like:

• The pump is functioning, but the tire still remains flat

That suggests there may be a leak or some other problem.

Finnish has no articles like a, an, or the.

So:

• pumppu can mean a pump or the pump
• rengas can mean a tire or the tire

The exact meaning comes from context.

In this sentence, English would naturally say:

• The pump works, but the tire remains flat

because both items are understood in a specific situation. But Finnish does not need separate words for that.

The word order here is the most neutral and natural one:

• Pumppu toimii, mutta rengas pysyy tyhjänä.

Finnish word order is more flexible than English, but changing it usually changes the emphasis.

For example:

• Rengas pysyy tyhjänä, vaikka pumppu toimii.
  = The tire remains flat, even though the pump works.

That version puts more focus on the tire staying flat.

But the original sentence is a very normal, straightforward way to say it.

The sentence is simply making a basic contrast:

• the pump works
• the tire still stays empty

Nothing more specific is needed unless the speaker wants extra detail.

For example:

• Pumppu toimii hyvin, mutta rengas pysyy tyhjänä.
  = The pump works well, but the tire remains flat.

That is also possible, but it adds information not present in the original.

So Pumppu toimii is short, natural, and complete.

Yes. Rengas can also mean ring or loop in other contexts.

Examples:

• sormus on rengas = a ring is a ring-shaped object
• olympiarenkaat = the Olympic rings

But in a sentence with pump and empty, the meaning is clearly tire.

Context usually makes this obvious in Finnish.

Yes, learners often compare pysyä and jäädä.

Both can relate to a continuing state, but they are not exactly the same.

• pysyä = stay / remain
• jäädä = be left / remain behind / end up staying

Here, pysyä is the better choice because it describes the tire continuing in the same state:

• Rengas pysyy tyhjänä = The tire stays flat

If you used jäädä, the nuance would be different and less natural in this context.

So pysyä is the most straightforward verb for stays/remains here.

A very literal translation would be:

• Pump works, but tire stays empty

A more natural English translation would be:

• The pump works, but the tire stays flat
• The pump works, but the tire remains flat

The literal version helps you see the grammar, while the natural version helps you understand how English would usually express the same idea.