Sen. Harrison A. Williams Jr. (D-N.J.), fighting for his political life after conviction of Abscam bribery and conspiracy charges, told his Senate colleagues yesterday that he is guilty of nothing more than "bad judgment" and an excess of zeal in trying to help two old friends. than "bad

Testifying before the Senate Ethics Committee, which is considering whether to recommend expulsion from the Senate or some other action against him, the four-term New Jersey Democrat said he already would have resigned from public office if he thought he had done anything wrong.

"But I tell this committee under oath," he said, "that while I may have been guilty of errors in judgment, while I may have crossed over the line which divides appropriate service to constituents from excessive boasting and posturing, I never engaged in any illegal conduct, I never corrupted my office and I never intended to do anything that would bring dishonor to the Senate."

Williams, 61, was convicted May 1 on all nine counts of a criminal indictment charging that he had agreed to trade his influence as a public official for a hidden share of a $100 million loan from an undercover FBI agent posing as a Arab sheik.

Williams now is waiting for a ruling from U.S. District Court Judge George C. pratt on the government's conduct of the Abscam investigation that led to his indictment and conviction. His lawyer in the Senate proceedings, Kenneth Feinberg, argued yesterday that the Ethics Committee should delay any recommendation to the full Senate until after the Pratt ruling, which is not expected until October. The committee tentatively has decided to vote on Williams' future at a meeting Aug. 24.

Last Friday, in a judgment that could have given Williams no comfort, Pratt rejected the pleas of four House members who asked that their Abscam convictions be overturned on many of the same grounds Williams has cited in a separate hearing before the judge. In a lengthy opinion praising the Abscam investigation, Pratt went out of his way to attack Williams' conduct.

Williams may also have gotten little comfort out of yesterday's proceeding before his six colleagues on the Ethics Committee. In a 30-minute, prepared statement, he laid out the thrust of his defense: that he had no "criminal intent" in any of the things he said and did that were captured on videotape by Abscam undercover agents.

The tapes, two of which were replayed yesterday, showed Williams discussing with the "sheik" how he could help get government contracts for titanium and how he could hide an 18 percent interest in a titanium mine to be developed with the "sheik's" loan.

But after Williams had made his case, there were a few questions from the other senators and most of these, by committee Chairman Malcolm Wallop (R-Wyo.) and Sen. Mack Mattingly (R-Ga.), were critical.

Williams said he became involved "in this unfortunate affair" because two longtime friends from New Jersey sought his help in arranging financial aid for a failing business venture. Although he increasingly came to consider the whole venture "pie in the sky," Williams said, he went along with a "script" that called for him to boast of his influence in the Senate and ability to obtain government contracts in order to convince the "sheik" to make the loan.

Williams insisted, as he did at his trial, that he received nothing for these efforts. Confronted with excerpts from the tapes showing him discussing how to conceal his interest in the venture, Williams repeatedly given him were worthless and that he merely was waiting for his friends to come to their senses about this "pie in the sky" undertaking.

"I certainly can't defend a lot of that talk of mine," he said when asked by Mattingly whether the tapes ought to be shown to incoming senators as an example of acceptable behavior. "But I broke no laws. I behaved in a way I don't like . . . I'm too old in life to learn this lesson, to be tough and not soft on your friends."