Maryland Gov. Harry Hughes issued an emergency order raising the truck-weight limit on all state roads yesterday, accomplishing with his executive powers something that he failed to push through the last session of the legislature.

Hughes, who had been pressured by striking independent truckers to move the state truck-weight maximum up to the federal standard of 80,000 pounds, signed the directive at a time when the truckers' protest appeared to be sputtering to an end.

The governor said his main purpose in raising the present 73,200-pound limit was not to appease the truckers but rather to save diesel fuel. He noted that diesel fuel is almost identical to home heating oil, of which there is expected to be a shortage next winter.

"We had a study done by the Stanford Research Institute that showed that allowing the truckers to carry the extra three tons would save 575,985 gallons of diesel fuel in the state each month," said Regina Friedlander, Hughes' deputy press secretary. "If refined into heating oil, that's enough to heat the city of Cumberland for the entire winter."

The emergency order raising the truck-weight limit will take effect at 12:01 a.m. Tuesday if it is first approved by the General Assembly's administrative, executive and legislative review committee, a panel of 10 state senators and delegates. It will remain in effect until Oct. 1.

Before issuing the order, Hughes met with the review panel and found that he had the support of at least eight of its 10 members.

During the last session of the General Assembly, a similar measure, backed heavily by the Hughes administration, was the source of an unusually bitter fight and eventually was killed by a Senate filibuster on the last night of the three-month session.

Opponents of the bill charged that the heavier trucks would cause costly damage to the state's highways and create burdensome traffic problems in city neighborhoods that contain trucking terminals.

But Hughes, who rarely interfered in the legislature's affairs during his first session, disputed those claims and argued that the economic benefits of the heavier trucks made it essential that the measure be passed. As the session neared an end, Hughes called several senators up to his State House office and pleaded with them to support the measure and kill the filibuster.

"The lobbying was really something," said Sen. Thomas V. (Mike) Miller Jr. (D-Prince George's). "It was the only time all year that he personally asked me for a vote. Of course, I was inclined to go along with it anyway."

The two leaders of the last-day filibuster - Sens. Howard Denis (R-Montgomery) and Arthur Dorman (D-Prince George's) - yesterday disagreed on the merits of Hughes' emergency order.

"I think it's bloody outrageous to raise the weight limits," Denis said. "Hughes is doing indirectly what he could not do directly. It's not so much that he's comming in through the back door as climbing through the window. He succumbed to a powerful lobby to accomplish something contrary to the public interest."

Denis urged Hughes to call a special legislative session to consider the truck-weight order, and he called the governor's action an abuse of power. "At this time," Denis added, "I would vote to take away the governor's emergency powers. He has demonstrated that he should not have them."

Dorman, on the other hand, said that "circumstances have changed," since the end of the session. "I have mixed feelings now," he said. "I can see making some concessions in this area, but I certainly wouldn't open up the heavier trucks to all roads."

The emergency order allows the use of 80,000-pound trucks on all state roads except those that state highway and local road officials decide cannot carry the extra load.

In issuing the directive Hughes said that Maryland was one of only six states in the country with a weight limit below 80,000 pounds and one of only to such states along the eastern corridor from Maine to Florida. The striking independant truckers made Maryland's restrictive regulations an issue during their three-week protest, claiming that it forced them to travel out of their way to carry goods and produce to markets along the East Coast.

Two weeks ago, when the truckers first raised the issue with Hughes, he said he was reluctant to raise the limit because it might appear that he was accomplishing by executive fiat something that he had lobbied hard but unsuccessfully for in the General Assembly. "Our feeling now is that the situation merits emergency action," said his aide, Friedlander. "We in no way intended to interfere with the normal legislative process."

In neighboring Virginia, meanwhile, the truck-weight debate continued yesterday as independent truckets and leaders of the state's Farm Bureau Federation asked Gov. John N. Dalton to raise the maximum there from 76,000 to 80,000 pounds. J. D. Brown, president of the Virginia Independent Truckers Association, told Dalton that the increase would make up for the higher fuel prices truckers must pay.