Little Maurice Cheeks pumped new life into the ailing Philadelphia 76ers today and nursed them to a thrilling 92-90 victory over the San Antonio Spurs, forcing a seventh game in their Eastern Conference semifinal NBA playoff series.

Cheeks who sat out the first 7 1/2 minutes of the final period because he had been ineffective, entered the game and scored seven of Philadelphia's last 11 points, including the winning basket with 10 seconds to play to even the series at 3-3.

The seventh game will be played Wednesday in San Antonio, the winner to meet the Washington Bullets for the conference title.

The 76ers were down by 13 points with 11 minutes to play when they finally got going and outscored the Spurs, 12-2, to close the margin to three points.

With Henry Bibby and Eric Money stumbling about and missing 11 of 15 shots between them, the 76ers still were able to make up ground, mainly because the tandem of 7-foot-1 Caldwell Jones and 6-11 1/2 Darryl Dawkins was mowing down the Spurs inside.

Finally, with the capacity Spectrum crowd of 18,276 screaming in unison, "We want Cheeks! We want Cheeks!", Philadelphia Coach Billy Cunningham turned to the 6-1 rookie.

Entering the game with 4:24 to play and Philadelphia down 84-81, Cheeks drilled in a wide-open 23-footer to cut the lead to one.

A minute later, after two San Antonio turnovers and a missed shot, Cheeks hit a 20-footer to give the 76ers their first lead of the game since early in the second quarter.

"I was so open because they kept double-teaming Doc (Julius Erving)," Cheeks said. "Those are the shots you have to make."

But Cheeks saved his biggest basket for later. The lead changed four times before San Antonio went ahead, 90-89, on an 18-foot jump shot by guard James Silas with 20 seconds remaining.

Philadelphia called a timeout and set a play for Erving.

"The shot was designed for Doc to work one on one against (George) Gervin," Cheeks said. "If he got double-teamed, he was to look for me at the foul line."

Silas left Cheeks to double-team Erving as soon as the ball was passed in, but no one picked up Cheeks and he slid down the lane. Erving spotted him and Cheeks scored the basket that put the 76ers on top, 91-90, with 10 seconds remaining.

San Antonio called time to set a play for Gervin, but Cunningham put his best defender, 6-9 Bobby Jones, on him and Jones knocked the in-bounds pass away from Gervin and out of bounds.

Gervin-in-bounded the ball this time and with three seconds left, Silas missed an awkward off-balance running one-hander and Gervin was called for a loose-ball foul, his sixth personal of the game.

After the ball was in-bounded, Mike Gale fouled Cheeks right away in the back court. With three chances to make two with two seconds left, Cheeks made only one shot. San Antonion rebounded his miss and called time with one second left.

With Gervin fouled out, the Spurs ran a play that got Mark Olberding a jumper from the corner. But the shot went in and out as the final horn sounded.

The 76ers have now come from being down three games to one in this series to within one victory of advancing to the conference final against the Bullets. Going into the fourth period, however, it looked like the Spurs had this game well in hand.

Philadelphia went scoreless for 5:07 of the third period and made only five or 22 shots in the quarter. But San Antonio could not put away the 76ers.

The Spurs, in one stretch of the period, turned the ball over five times in a row and on eight of 11 possessions and still were able to increase an eight-point lead to nine.

Going into the final 12 minutes down 11 points, Cunningham said, "I told them we couldn't play any worse offensively and we were still in it, so just keep the defensive pressure on."

Gervin playing only 23 minutes because of foul trouble definitely hurt the Spurs, though he did manage 21 points.

Silas led the Spurs with 27 points, but they got nothing from their centers as Billy Paultz and Mike Green missed all nine of the shots they took. Green misfired on seven.

Caldwell Jones, playing forward so Cunningham could get Dawkins in the game at the same time, led the 76ers with 20 points, 17 rebounds, three assists and three blocked shots.

"The pressure is definitely on San Antone now," said Dawkins, looking ahead to the seventh game. "They were saying this series would never go seven games. That's got to be haunting them." CAPTION: Picture, San Antonio's George Gervin is dismayed at fouling out. UPI