VALENCIA, Spain — Over the past two years, Ana María Molina Cuevas, 36, has worked five shifts a week in a ceramics factory on the outskirts of this city, hand-rolling paint onto tiles. But at the end of the month, she often went unpaid.

Still, she kept showing up, trying to keep her frustration under control. If she quit, she reasoned, she might never get her money. And besides, where was she going to find another job? Last month, she was down to about $130 in her bank account with a mortgage payment due.

“On the days you get paid,” she said at home with her disabled husband and young daughter, “it is like the sun has risen three times. It is a day of joy.”

Mrs. Molina, who is owed about $13,000 by the factory, is hardly alone. Being paid for the work you do is no longer something that can be counted on in Spain, as this country struggles through its fourth year of an economic crisis.