For the first five weeks, Jimmy McIntyre didn't tell anyone he was on a hunger strike, not his lawyer, not even his jailers at the Arlington County Jail. His purpose, he said later, was to make sure people took him seriously.

Last Friday, McIntyre, a 32-year-old prisoner being held on charges of rape and burglary, was moved from Arlington, headed for a state mental facility. It is not where he is likely to get the treatment for post-Vietnam syndrome he says he has been fasting for. It isn't where his lawyers thought he should go. It isn't even where a circuit court judge had ordered him to go two days before. But it was apparently the only place that would take him.

Meanwhile, McIntyre says he will stay on his hunger strike until he is allowed to see a doctor with expertise in post-Vietnam syndrome -- or until he lapses into a coma that for the first time would allow his lawyers to ask the court to order intravenous feeding.

McIntyre's hunger strike has become a serious issue, although not for the reasons he intended. By refusing to eat, McIntyre, a Vietnam veteran with a 10th-grade education and a history of drug addiction, is an unusual, unwelcome and perplexing problem for a system that for weeks has been unable to figure out what to do with him.

"It's the reverse of Karen Ann Quinlan," said Mark Yeager, a Fairfax attorney appointed to defend McIntrye. "We're not talking about mollycoddling prisoners, we're talking about basic human life."

Arlington Circuit Court Judge Charles S. Russell says McIntyre's case points to a need for new laws allowing medical treatment of prisoners undergoing psychiatric evaluation. "It's atrocious," said Liam O'Grady of Arlington, McIntyre's other court-appointed attorney. "There is obviously a gap in the system."

"The thing that concerned me all along was that somehow Mr. McIntyre would fall between the bureaucratic cracks and that by the time anybody got around to acting, he was going to be dead," said Yeager.

At the center of all the legal confusion is McIntyre himself. By Friday, he had lost almost 40 pounds, one-quarter of the 160 pounds he weighed when he arrived at the Arlington jail last September. By his account, the 5-foot-7 McIntyre began to fast Oct. 16, refusing all solid foods, accepting only coffee with sugar. His face became pale and drawn, his movements weak and shuffling. If McIntyre continued, a doctor told O'Grady last week, he would be unable to move in another week.

Eventually, like the Irish hunger strikers whose tactics he has adopted, McIntyre is heading for a coma. Once unconscious, he will be legally "incompetent" to care for himself. Yeager, appointed his guardian Friday, would be able to have him fed intravenously.

McIntyre has made his demands clear from the start. He wants to be examined by a psychiatrist familiar with post-Vietnam syndrome, the term increasingly used to describe delayed reaction to the stress suffered by combat soldiers. McIntyre thinks the syndrome might explain many of his problems.

"I'm not using it for a defense," he said. "I just want to know about me. It's a last resort to try to get some help."

McIntyre was 19 when he served as an infantryman in Vietnam in 1967 and 1968 during the Tet offensive. It was then that he started using drugs, he said, a habit that by 1980 had included narcotics, barbiturates, amphetamines and other drugs.

There were early signs of trouble after McIntyre left the Army but, by his account, his first brush with the law was in 1975 when he served five months for burglary in Alexandria. In 1980, he saw a Tom Snyder program on the Veterans Administration's Vietnam Outreach Program, signed up and was admitted to the VA hospital in Washington.

A September evaluation by a VA doctor showed him to have test scores "consistent with a cerebral dysfunction" and a personality that was "nondirective, detached, withholding, cynical, hostile." He should, said the doctor, be "carefully watched." When he checked himself out of the hospital in December, the final VA report concluded: "Prognosis guarded."

McIntyre said he didn't learn of any of these problems until the spring of 1981, when he was sentenced on burglary charges in Alexandria. There a judge gave him an alternative sentence to Second Genesis, a drug rehabilitation program. McIntyre lasted 10 minutes in the program, O'Grady said. Asked to walk a dog, he fled into a wooded lot in Crystal City. He lived there for a month last summer, sleeping in a car.

Finally, he was arrested by Arlington police and charged with rape, a string of burglaries and other offenses. He has also been indicted for another rape, an attempted rape and two burglaries in Fairfax, also committed last summer. A month after he was jailed in Arlington, he decided he needed psychiatric help.

"I don't need anyone to tell I'm a slimy dope fiend," he said, explaining that he believes drugs are only a part of his trouble. "It's time to inventory myself. I know my life isn't right, but it's no good not getting anyone else's opinion."

When he was first informed of McIntyre's demands, O'Grady, his Arlington attorney, called a dozen psychiatrists, including the one at the Veterans Administration who diagnosed McIntyre a year ago as someone who "may have significant psychiatric problems." So far, no doctor has offered his time, either because McIntyre has no money or for his own "personal" reasons, said O'Grady.

By order of Judge Russell, McIntyre has seen a psychiatrist -- but it was not one with any familiarity with post-Vietnam syndrome, O'Grady said. The report filed with the court by Dr. George D. Weickhardt said McIntyre was paranoid, wanted to die and needed further psychiatric evaluation to determine whether he is fit to stand trial.

That report led to Russell's order for an official evaluation of McIntyre at Central State Hospital in Petersburg. As of Thursday night, Russell, Arlington Sheriff James Gondles, Assistant Commonwealth's Attorney Arthur Karp, O'Grady and Yeager expected McIntyre to be on his way to Petersburg Friday.

But that was not to be. Word came back from Central State that unless McIntyre could be declared "incompetent" for purposes of forced medical treatment, they would not accept him. In the meantime, however, Russell had denied a motion filed by McIntyre's attorneys to declare him "incompetent" for purposes of medical treatment. Russell said McIntyre was competent to seek medical treatment; the problem was he had chosen not to.

"There have been a rash of decisions to the effect that you simply cannot force feed people," said Russell later. "If you do, you are guilty of assault."

Court officials also discouraged the lawyers from pursuing civil "involuntary" commitment for McIntyre as long as he has criminal charges pending against him.

By early Friday, McIntrye was still looking for the psychiatric treatment he'd been seeking, still fasting and still in the Arlington jail, where Gondles and jail officials were becoming increasingly anxious to get him moved. A series of phone calls finally produced a receptive answer from Western State Hospital, which agreed to take him as an exception, even though Western State does not usually examine prisoners for competency to stand trial.

"It's a start, but it's not what I want," said McIntyre as he prepared to leave Arlington Jail for the trip to Western State. And until he does get the kind of help he seeks, or until he falls into a coma, McIntyre said he will continue to refuse food.