ADC10 jumbo jet that apparently left Los Angeles with only two of three fuel tanks full made an emergency landing in Tampa Sept. 6 as its engines sputtered to a halt, officials said yesterday.

The Federal Aviation Administration is investigating the captain, flight engineer and a mechanic involved with the Pan American World Airways flight. Pan Am officials said the engineer, whose duties included overseeing fueling, has been suspended 30 days without pay.

The jet, bound for Miami with 139 passengers, was over the Gulf of Mexico Sept. 6 when the pilot reported his fuel gauges registering dangerously near empty, the FAA said.

Air controllers diverted the jet to Tampa. "When the plane landed, all three engines were running. But when it was taxiing to the terminal, the engines started to quit. It was a critical fuel problem," a Pan Am spokesman said.

FAA spokesman Jack Barker said one of the jet's three fuel tanks apparently was not filled before takeoff. With one-third of the 110,000 pounds of necessary fuel missing, he said, the flight could not have reached Miami.

A preliminary investigation found that a measuring gauge in one tank had been broken, Barker said. Such a malfunction does not ground a plane because a mechanic is expected to check fuel with a dipstick, although a mechanic apparently checked one of the full tanks and not the others, he said