Esta mañana el coche no quiso arrancar, así que la mecánica lo revisó durante media hora.

Spanish often uses the definite article more than English does. In this sentence, el coche simply means the car.

You usually need the article with a specific noun:

• el coche
• la casa
• el libro

English sometimes drops the article in places where Spanish does not, but here both languages use it naturally: the car / el coche.

In Spanish, expressions of time like esta mañana, ayer, hoy, esta tarde, and anoche usually do not need a preposition.

So:

• Esta mañana = This morning
• Esta tarde = This afternoon
• Ayer = Yesterday

Using en here would sound unnatural in standard Spanish.

Literally, quiso arrancar means wanted to start, because quiso is the preterite of querer.

But with machines, cars, computers, engines, etc., Spanish often uses querer + infinitive in a figurative way to mean that something wouldn’t do something.

So:

• El coche no quiso arrancar literally = The car didn’t want to start
• natural English meaning = The car wouldn’t start

This is a very common and idiomatic use.

Because no quiso arrancar is a very natural idiomatic way to talk about a machine failing to do something.

Compare:

• El coche no quiso arrancar = The car wouldn’t start / idiomatic and common
• El coche no pudo arrancar = The car couldn’t start / more neutral, more literal idea of inability

Both can work in some contexts, but no quiso arrancar sounds especially natural when talking about a car that is being uncooperative.

With cars and engines, arrancar is the usual verb for to start.

Examples:

• El coche arranca bien = The car starts well
• El motor no arranca = The engine won’t start

By contrast:

• empezar
• comenzar

usually mean to begin in a more general sense, not specifically to start a car engine.

Quiso is the preterite of querer.

The preterite is used because this is a completed event in the past:

• This morning, the car failed to start at that moment/situation.

So:

• quiso = wanted / here, idiomatically would
• no quiso arrancar = wouldn’t start

The sentence tells a sequence of completed past events:

1. the car wouldn’t start
2. the mechanic checked it

That is why the preterite fits well.

It can, but here la mecánica means the female mechanic.

Spanish distinguishes:

• el mecánico = the male mechanic
• la mecánica = the female mechanic

It is true that la mecánica can also mean mechanics as a field, depending on context. But in this sentence, because it is followed by lo revisó and refers to a person doing the checking, it clearly means the female mechanic.

Yes. If the mechanic were male, it would be:

• ... así que el mecánico lo revisó...

Spanish changes many profession nouns to match gender:

• el médico / la médica
• el profesor / la profesora
• el mecánico / la mecánica

Lo is a direct object pronoun meaning it here. It refers back to el coche.

So:

• La mecánica revisó el coche = The mechanic checked the car
• La mecánica lo revisó = The mechanic checked it

Since coche is masculine singular, the pronoun is lo.

Because revisar takes a direct object, not an indirect one.

You are checking the car directly:

• revisar algo = to check something

So:

• el coche is the direct object
• the correct pronoun is lo

Compare:

• Lo revisó = She checked it
• Le dio una llave = She gave him/her a key

In standard Spanish, le is normally for indirect objects, not direct objects like el coche.

In a normal conjugated verb structure, object pronouns go before the verb:

• Lo revisó
• La vio
• No lo encuentro

They attach to the end only with:

• infinitives: revisarlo
• gerunds: revisándolo
• affirmative commands: revísalo

Since revisó is a fully conjugated verb in the preterite, lo goes before it.

Not exactly. Revisó means checked, inspected, or looked over.

So:

• revisar = to check / inspect / examine

It does not necessarily mean the mechanic fixed the car. It only tells us she spent time examining it.

If the idea were repaired, Spanish might use verbs like:

• arreglar
• reparar

Durante media hora means for half an hour or more literally during half an hour.

• durante = during / for, when talking about the duration of an action
• media hora = half an hour

So:

• lo revisó durante media hora = she checked it for half an hour

This is a very natural way to express duration.

Sometimes learners try that because English uses for, but durante media hora is the more natural choice here.

Por media hora can appear in some contexts, but for simple duration of an action, durante is usually safer and more standard:

• Estudió durante dos horas
• Esperamos durante media hora

So in this sentence, durante media hora is the best choice.

Because the sentence describes completed events in a sequence.

• el coche no quiso arrancar = the car wouldn’t start
• la mecánica lo revisó = the mechanic checked it

These are viewed as whole, finished actions in the past, not as background or ongoing situations. That is exactly what the preterite is commonly used for.

Así que means so, therefore, or so then. It introduces a consequence.

• El coche no quiso arrancar, así que la mecánica lo revisó.
• The car wouldn’t start, so the mechanic checked it.

It is not the same as porque:

• porque = because → gives a reason
• así que = so → gives a result

Compare:

• Lo revisó porque no arrancaba. = She checked it because it wasn’t starting.
• No arrancó, así que lo revisó. = It didn’t start, so she checked it.

Yes. Spanish usually leaves out subject pronouns when they are not needed.

So instead of saying:

• ... así que ella lo revisó

Spanish normally just says:

• ... así que lo revisó

The verb ending -ó already tells you it is he/she/it in the preterite, and the context tells us it refers to la mecánica.

Yes. Arrancar has several meanings depending on context.

Common ones include:

• to start an engine or vehicle
  
  • El coche no arranca
• to pull out / tear out / yank out
  • Arrancó la página
• sometimes to set off or get going
  • Arrancamos temprano

In this sentence, because the subject is el coche, the meaning is clearly to start.

The word order is very natural and standard:

• Esta mañana el coche no quiso arrancar, así que la mecánica lo revisó durante media hora.

Spanish does allow some flexibility, but this order is neutral and easy to understand:

1. time expression
2. subject
3. verb phrase
4. result clause

You could change parts for emphasis, but the original is the most straightforward version for everyday Spanish.