It was 4 a.m. one Saturday morning last month and Ray Marshall didn't want to go into the Labor Department's auditorium and tell the press the coal talks had broken down. Again.

Marshall was fatigued and finally discouraged. On only a few hours sleep, he had spent the previous 2 1/2 days in an intensified round of bargaining and caucusing, and had been optimistic that an end to the 73-day-old strike was in sight. He had been shuttling between the White House, where the coal operators were waiting in the Roosevelt Room, and his office, where the bargaining council of the United Mine Workers was camped out.

Now all the work and all the hours seemed for naught. And the beleaguered Marshall was tired of black coffee, tired of the spareribs dinners the staff was ordering for this son of a Louisana tenant farmer.

This endless night the secretary didn't even try to relieve the tension with a Bob Newhart routine. (His imitation is unrivaled, says his staff.) Everything was unraveling and he hated to say that out loud.

"Folks," said Marshall, hesitating a little as he faced the bleary-eyed press corps, "sorry, we can't reach an agreement. The bargaining council voted down the last offer, 39-0. It looks like it's not going to be possible for us to have a negotiated settlement."

But the painful night was not over for Marshall. As he wrestled with the coal strike, the first major crisis during his 14 months as Labor secretary, he also had been coping with a personal ordeal. Within a five-week period, his son Christopher, 15, had two operations for cancer. On January 30, Chris had an arm and shoulder removed because of the disease, and underwent a second operation on March 2, after it was discovered the disease had spread to his lungs.

The morning of the pre-dawn press conference, Marshall went home, spent some time with Chris, one of his five children, and was back in the office before 9 a.m.

Yesterday the 160,000 striking UMW members voted on the latest contract offer, the third since Dec. 6. Cautious about the outcome, Marshall prepared two statements, one grateful, one not. By early evening the prospects for using the grateful one looked dim.

"It's been a pretty hard time," said Marshall, 49, earlier this week. To his friends Marshall is known as a man who has two loves, his work and his family. Despite simultaneous crises in both areas, publicly Marshall has not lost his control, congeniality or optimism.

"We were shocked about Chris, partly because it was so sudden, but also because at every turn in the process, things were pretty bad. You think a pain in the arm is a muscle problem or a sprained ligament but it turned out to be cancer. It was a shock," said Marshall, his voice soft and level but the words impeded by his emotion.

The people who saw the most of Marshall, however saw only his stoic side. "I would go home some nights after those negotiations and Helen would ask me what was disturbing me," said Robert Strauss, the chief U.S. trade negotiator who was part of the White House coal strike team. "I told her I was thinking about Ray Marshall, and how that guy was under the tremendous weight of the president putting his confidence in him on the strike matter, plus the burden of his lad. I couldn't do it. And I've always thought of myself as a strong man. He was unflappable, he never showed the tension."

Stuart Eizenstat the adminstration's domestic affairs adviser, noted, "I saw him at countless meetings. He looked fresh, he never showed any strain. And his mind never wonders and you think it would at a time like this."

Patricia Marshall, shy and soft-spoken, has seen this strength before in her husband in their 31 years together. "Ray has never given into any kind of pressure," she said.

His particular resilience and discipline evolved from his own emotional battles as a child. He was very poor spent five years in an orphanage, and lied to get into the Navy at age 15. By the time he was 48, and selected for the Cabinet, Marshall was a well-established economist at the University of Texas, with an armful of books to his credit and a 75-acre ranch. He believes anybody can beat the odds.

By many different people, Marshall is considered a rare bird. George Meany once introduced Marshall to Alexander I. Solzhenitsyn as one of the few professors in the United States who understood working people. Some people find it surprising, given his background, that he developed what friends call a "guiltless" sensitivity to race relations and focused much of his professional interests on the plight of minorities.

Not everybody likes Ray Marshall, his views, his performance at Labor or his strategy during the coal strike. But he deals with criticism and tough situations with examples of courage he has borrowed from novelist William Faulkner, the late Earl K. Long, the governor of Louisiana, and the apostle Paul.

It's Faulkner he quotes, especially from the writer's Nobel Peace Prize speech: "I believe that man will not merely endure: He will prevail." Making Things Simple

"I don't remember not working," said Marshall, putting aside a piece of wire copy he had been doodling on and settling into a corner of his office couch.

Coming from this Labor secretary that statement in not flip but factual. Marshall has the ruddy complexion of an outdoorsman, which he has been at least by hobby most of his life. This afternoon he is not wearing the cowboy boots he wears at least twice a week but a pair of brown oxfords, with a brown and whife suit.

Marshall was born in Oak Grove, La., where his father, Thomas, was a tenant farmer. Marshall was Freddie Ray then and he picked cotton and sugar cane. He spoke of his father as a strong man who rejected the fundamentalist religion of North Louisiana as irrational and emotional, and his mother, Virginia, as a sensitive, largely self-taught woman, who gave him his first lessons in race relations.

"We had black neighbors and my mother said to address them 'Yes, ma'am.' The white neighbors didn't like that and criticized (her) but I didn't develop any fears because of that criticism," said Marshall.

When Marshall was 11, his mother died suddenly of blood poisoning and the five children went to live in the Mississippi Baptist Orphanage in Jackson, where the family had by now moved. Thomas Marshall, the secretary's younger brother, who now works for the Department of Agriculture here, recalled, "He kept the brood together. We griped about the work we had to do but Ray was energetic. He got up at 4 a.m. to milk the boilers of the laundry. And he was cows, and he operated the engines and smart. I overheard the teachers say that he knew more than they did."

The education and work procedures at the orphanage were bound into a strict religious code, and Marshall viewed it skeptically. "I tried to learn all I could about Christianity and the brotherhood of man.But what disturbed me was the contrast between what they did and what they were saying, particularly on race matters and materialism. The preacher would say, 'This is the way God intended things. Do you find cows mixing with horses or birds mixing with rabbits.' And I asked, 'have you ever heard of black cows mixing with white cows?'"

Eventually Marshall decided he wanted more independence and when he was 15 he ran away from the orphanage, worked briefly making false teeth, and then joined the Navy, serving as a radio operator in the Pacific.

After World War II, Marshall returned to Jackson, got his high-school equivalency diplomac, enrolled in Hinds Junior College, where he met his wife, and then earned a degree from Millsaps College. At one point, Marshall considered a political career "to address the issues of the disadvantaged." A professor told, "Look, life isn't that much fun down here and politics is about the only entertainment we have. We don't want to hear serious talk. So think about that."

Marshall took his interest to the classroom where his views as a faculty member of the University of Mississippi and Louisiana State University in the 1950s attracted the White Citizens' Council. They called him a "scalawag and troublemaker." But he survived in the environment, recalled Bernard Sliger, a colleague who is now president of Florida State University, because, "Ray never irritated people. It wasn't felt that he was an outsider and he was always calm and logical. He always smiled."

From his experiences in the South, Marshall picked two people from whom he learned valuable lessons - William Faulkner, whom he met in the early '50s, and Earl Long. "I really didn't read Faulkner until I was in Finland on a Fulbright in 1955 and 1956. It was a writing style I was not used to because I was accustomed to scanning books and papers. I told Faulkner this and he said, 'I work hard at my craft, I don't want you to scan it.' And we talked about fear and courage, and he said, 'The only thing you can do well when you fear is run, and if you are running, you are not true to yourself.'"

Again, it was courage and style that Marshall learned from Long, two-team governor of Louisiana. "I certainly didn't agree with everything he stood for. But he showed you could dramatize the simple things, you could get your point across and still be outrageous," said Marshall.

The secretary, it is quickly noted, has been just the opposite: shy, lowkeyed, methodical, and, before the coal strike, often overlooked. "Yes," said Marshall. "But I am trying to make things simple." No Holding Back

As secretary of Labor, Marshall has accomplished many of his goals. Under his administration, the overall unemployment rate has dropped from 7.3 in January, 1977, to 6.1 percent last month. The overall black unemployment rate has dropped in the same period from 13.1 to 11.8. Yet the black teen-age unemployment rate, which has hovered around 40 percent, has barely changed.

He has doubled public service jobs to 725,000, gotten a sizable jobs component in the welfare reform measure and was the administration's strongest point man in House passage of the Humphrey-Hawkins jobs bill. He also has lost on a couple of pieces of legislation.

His internal staffing also has drawn praise; there are a number of highly placed blacks and his assistant secretary for manpower, Ernest G. Green, is black.

He's pleased.

Others are not. Charles Bailey of the National Right to Work Committee, called Marshall's record "abominable." Sen. Orrin Hatch (R-Utah), a member of the Committee on Human Resources, formerly Labor and Public Welfare, said Marshall's a "decent, scholarly man but as a secretary he is biased to big labor on almost all issues and he performed poorly in the coal miners' strike. He wasn't forceful enough."

But then again some are pleased. "I'm not criticizing Marshall when I criticize President Carter," said Jerry Wurf, president of the nation's largest public employe union, who has denounced some of the Carter's urban approaches. "Marshall is one of the best appointments, forthright and honorable. We know he has to compromise and when we don't get everything, it's not his fault." Another critic of the administration, M. Carl Holman, president of the National Urban Coalition, said, "He understands. We've lost some fights but when he is attacked as a liberal in the Cabinet, I consider that a good sign."

Rarely does Marshall get ruffled by criticism, defensive, yes, but, rarely angry. Only once in the last two months, with the monumental professional and personal pressures, does the staff remember him angry. Evans and Novak wrote a column giving Robert Strauss the credit as the chief strategist in the negotiations. Marshall exploded. Strauss has since said Marshall called the shots.

And, it was to Strauss that Marshall turned the night President Carter announced the contract agreement and said, "No is more relived than I that this is settled. Now I can get back and devote more time to my personal decisions."

In his office, Marshall is talking about fear, that fears are self-imposed. And about sleep, that needing a lot of sleep is a state of each person's mind. He hasn't had that much sleep lately.

"One of the ways I have been able to deal with the coal thing and the shock with Chris as been Chris' own attitude. We discussed the different treatments, whether chemotherapy is better immediately after surgery or should we wait. We talked about the unpleasantness that can come with the treatment. We haven't held any thing back from him," said Marshall.

When Chris was hospitalized during the coal strike, Marshall would visit him in the morning, again in the evening, and sometimes, at lunch. He came back encouraged as Chris learned to write with his other arm, learned to tie his shoes and put in his contact lenses.

"But the thing that has made it easy is his own strength. We decided that it doesn't help to get depressed," said Marshall. And he taught his son and the rest of the family his first principle, "Never to worry about things I cannot change."