تَوَقَّفَ السَّحْبُ سَاعَةً. كَانَ الصِّمَامُ يَحْتَاجُ إِلَى فَحْصٍ.
Pumping stopped for an hour. The valve needed inspection.
The first statement can naturally prompt: Why did pumping stop? The second then supplies an explanatory answer, allowing an analysis in terms of explanatory resumption (istiʾnāf bayānī). Separation without wāw reflects the implicit question-and-answer relation.
Yet adjacency alone does not guarantee this reading. The question must actually arise from the discourse, and the second clause must genuinely respond to it.