Was the federal-military machine running illegally last fall when it kept going after Congress cut its credit to buy merchandise, pay bills or meet payrolls?

Backers of a federal paycheck-protection bill say the government could be shut down legally this year if the Senate and House again play games with agency budgets. Hearings on legislation to keep federal salary money flowing -- regardless -- are going on this week before the House compensation subcommittee. Many subcommittee members represent civil servants who were temporarily short-changed in October.

Paycheck portection types want to prevent a repeat of the 1978 and 1979 fiscal follies. Both the Senate and House played chicken with agency budgets, refusing to clear them for the new fiscal year because of hang-ups over abortion-funding language.

That institutional blockage caused many federal agencies -- plus the Army, Navy and Air Force -- to run out of funds to pay anybody for work after Oct. 1, the start of the new fiscal year. Nearly a million civil servants got half paychecks, or were paid late, because agencies could not meet payrolls for services after that date. The crisis eventually was settled and people finally got paid. But some think the whole operation was illegal, and could force a legal shutdown of the government this October if the Senate-House budget fight is repeated.

Subcommittee Chairwoman Gladys N. Spellman (D-Md.) said there is a law on the books that prohibits Uncle Sam from promising to pay people money not already approved by Congress. The same statute, Spellman said, bars the government from asking personnel to "volunteer" for duty, pending settlement of any budget problems.

Spellman's subcommittee counsel cited Title 31, U.S. Code, Chapter 665, which says in part ". . . nor shall any such officer or employe involve the government in any contract or other obligation, for the payment of money for any purpose in advance of appropriations made for such purpose unless such contract or obligation is authorized by law. . . ." A strict reading of that could put the federal establishment on a legal furlough this fall, if the Senate and House hold up budgets, or unless Congress authorizes payment of salaries during such budget hang-ups.