After more than two years of threats, court fights and a rigid refusal to pay higher rates, Crystal City lost its natural gas today.

At 9:26 a.m. a remote-controlled valve, activated by reduced pressure and an $800,000 debt for back charges, closed itself and ended the flow of gas to this poor and predominantly Hispanic city of 8,107 in south Texas.

But so severe in the poverty here and so spare are the lives of many of those dwelling in it - and in whose name city officials refuse to pay increased gas rates - that even the cutoff of such a necessity had minimal immediate impact.

Along the rutted and unpaved roads that divide one family's shack from another's shanty, Carlos Lopez pointed to the front-yard faucet and garden hose that serves him and his wife with water and said, "I don't have hot water anyway. That's all I've got."

And for many of the elderly, living alone in their immaculately kept public housing duplexes, the loss of their gas was merely a return to the years of denial they experienced as field workers. "Long years ago we cooked outside, and when we went north they did not give us stoves either," said Benigna Aldava, 77, a former picker of grapes, cotton, celery and tomatoes. "We are used to it."

City officials reported no disruptions of municipal services, the schools had converted to electric stoves, there is no hospital here and the area's biggest employer, a Del Monte canning factory, has an independent gas supply.

So on a day with temperatures in the 90s and with the prospect of winter seemingly far away, city officials continued to blame their gas supplier, Lo-Vaca Gathering Co. of Houston, and the state government in Austin for their plight. Meanwhile, the mayor, the city manager and a councilman met in Washington to seek help.

"A lot of the people still feel it's political," said Councilman Rudy Espinosa, who answered "definitely" when asked if his La Raza Unida party had alienated state officials and thus been unable to get state help.

For this area was the birthplace of the party, whose name was roughly means "people together." In 1972, the party's gubernatorial candidate drew off enough traditional Democratic votes to nearly deny election to Democratic Dolph Briscoe who sits in the governor's office today.

Efforts to reach the governor's office for commment were unsuccessful.

Still, at the heart of today's cutoff was the nation's sharply increased energy costs and their impact on those of limited income. While the poor and the elderly have been strapped by those costs across America, it was here that the La Raza Unida-dominated city council drew the line and said no.

"We just don't have the means," said Espinosa. "We prefer balanced lives to balanced budgets. We had people who came in here and put down their welfare checks and still couldn't cover the gas bill," said Espinosa, referring to a brief period when the city did pass on the higher gas costs.

Lo-Vaca, which buys $100 million worth of gas a month for distribution to municipalities, industries and farmers in virtually the entire state, had contracted to supply Crystal City with gas at 36 cents for each 1,000 cubic feet. When costs incurred in obtaining gas rose, Lo-Vaca was granted higher rates by the Texas Railroad Commission, the state body. The rate is now more than $2 a thousand, and since early 1976 Crystal City, that regulates common carriers, including gas pipelines, has refused to pay.

By now the debt has risen to $800,000 - $100 for every man, woman and child in one of Texas' lowest income areas. Per capita income is $1,616 a year, about half of what it is statewide.

Many residents here still pay $10 summertime gas bills and usually $20 in the winter. If the city were passing on the full cost of the gas those bills would be more like $50 and $100. Such bills would rival the monthly income of many of those living here.

It is generally agreed that without outside help the city has virtually no chance of ever paying off the debt. (Three other Texas cities also pleaded the harship of poverty when rates were raised, but unlike Crystal City they put in escrow the difference between the old rate and the new, and their escrows now toral $2.5 million.)

Many of the workers are migrant farm loborers, and the tilting one-room homes up on cinder blocks here makes this city look like an underdeveloped country. More fortunate are those able to get houses in the city's public housing complex.

There, residents were given an opportunity to buy electric hotplates for $25. But those people, who live on either fixed pensions or low wages, will thus face increased electric bills.

Pura Martinez, 27 and the mother of six, says she does not know what she will do about cooking for her children, ranging in age from 8 years to 2 months. Her double hotplate is clearly inadequate, and there is no oven. As a result, she expects to switch the children from meat, tortillas, beans and potatoes to "baloney sandwiches." Her husband, Raoul, is a migrant field worker now in Wyoming. Their income is about $5,000 a year, and they pay $48 a month rent on their four-bedroom public housing duplex.

Mrs. Martinez blames local officials for the gas cutoff, even though she does not know how she would pay higher costs.

Benigna Aldava takes an opposite view. She blames Lo-Vaca and state officials and says "Lo-Vaca should rot with its millions." And as a group of visitors leaves her tiny home, she calls out, "Viva Crystal City! Always! Arrival."