Maybe some of Washington's investigators ought to be investigated themselves to find out why they are dragging their feet and neglecting to look in all the dark corners.

For openers, six weeks have now elapsed since the House Ethics Committee reluctantly agreed to start investigating the questionable financial and lobbying activities of House Speaker Jim Wright.How much has the committee accomplished in that time? Virtually nothing. It has yet to question a single major witness or even decide if it will hire an independent counsel, as it should.

Then there's the investigation into fraud and bribery in defense contracts. Initially, the FBI assured that no member of Congress is a target of the burgeoning investigation of fraud in defense contracts. But the agency may have spoken too soon.

Even if the nation's lawmakers turn out to be not be culpably involved in the current scandal, their hands are anything but clean when it comes to the Pentagon.

A few days ago, for example, The Washington Post told how Rep. Bill Chappell of Florida and Rep. Roy Dyson of Maryland forced the Navy to buy an electronic warfare system it didn't want. Guess where the firm making the system does much of its business. That's right - Florida and Maryland. What a coincidence!

Scripps Howard News Service later reported that two Washington representatives of defense contractors helped relieve Chappell and a business partner of nearly $300,000 worth of debts incurred in the development of a failed health club in Florida. Under a deal with a bank that had foreclosed on the property, the lobbyists took over the club for less than the outstanding notes, and the bank absolved Chappell and his partner of any responsibility for the debts.

Yet a federal ethics code warns officials against accepting "favors or benefits . . . which might be construed by reasonable persons as influencing the performance of their govearnmental duties."

Earlier, The Wall Street Journal reported how Chairman Les Aspin of the House Armed Services Committee and some of his colleagues forced the Army to buy hundreds of millions of dollars worth of ammunition trucks after the Army wanted to stop purchasing the vehicles. Aspin represents the state of Wisconsin. Now, guess where the firm making those trucks is headquartered. Good guess!

Besides pushing defense contracts for homestate firms, members of Congress are notorious for opposing Pentagon proposals to close obsolete military bases. The Pentagon estimates it could save $5 billion a year by closing such bases. As a column on this page notes, a study of 100 base closings since 1961 shows the areas involved ended up with 48 percent more civilian jobs than they lost. But that doesn't keep Congress from fighting efforts to close old, unneeded bases.

Then there's the recent study from Common Cause showing that the 62 members of the House and Senate serving on defense committees and receiving speaking and other such fees from top defense contractors got 71 percent of the total of such money paid to the whole Congress last year. They received almost three fourths of the money even though they account for only 12 percent of Congress' membership. It all added up to $521,310 that these defense committee legislators received from large defense firms. What an enormous potential for influencing lawmakers to put private interests ahead of the public good.

As Americans focus on the latest defense scandal, they shouldn't let themselves lose sight of the old and continuing Pentagon scandal - the one in which Congress is so deeply involved.