D.C. Mayor Marion Barry drove out to the shabby East Capitol Dwellings public housing project yesterday to tell tenants and specially invited political and community leaders the good news that the city will spend $18.2 million in federal funds to completely renovate the 557-unit project.

But it was good news many tenants say they have heard before, and it was not quite all the news. Barry did not tell the gathering that the federal government has given the city only $6 million of the $18.2 million and that the city is unsure when the renovations will begin.

The remaining $12.2 million is contingent on congressional approval of the fiscal 1981 budget for the U.S. Department of Housing and Community Development and thus is not absolutely assured. While city officials don't know when renovation work will begin, HUD says it will be at least a year before the first nail is driven.

Mary Mason, 52, longtime East Capitol Dwellings tenant who lives near the dingy cinderblock administration building where Barry spoke, did not attend yesterday's announcement. But the promises were familiar to her.

"We've heard so many times that they were going to do this and they were going to do that [but] the place is just deteriorating," Mason said. "They should condemn it. They aren't fit to live in," she said of the units in the 25-year-old project.

Bessie Carey, the project's representative on the city-wide Resident Council Advisory Board, said a majority of residents are fed up with what they see as continually unkept promises of better conditions.

"People are frustrated because they can't get anybody out fo fix the roofing, the plumbing, the plastering," she said. "People have gotten tired of complaining about their housing."

Barry, flanked by city housing director Robert L. Moore as they walked under umbrellas inspecting the project in yesterday's rain, promised there would be action this time, listing East Capitol as the first in a series of large public housing projects that will be renovated in the next five years under an ambitious city program.

At East Capitol, in fact, Moore said, the replacement of roofs and improvement in the heating system will begin this fall with federal funds separate from the $18.2 million announced by Barry yesterday.

The residents "will have reliable heat and hot water this winter," Moore promised.

That is good news for Carey, who said she has been heating water in her basement kitchen practically every day for years and lugging it upstairs to the bathroom. She said many of her neighbors go through the same routine.

The installation of new electric lines and water and sewer pipes leading into East Capitol Dwellings will begin in the spring, Moore said, but no schedule has been set yet for renovation of individual apartment units. Many tenants complained yesterday of broken stoves, falling plaster, large wall cracks, broken windows and cabinets that must be propped up with sticks.

East Capitol tenant George Marrow, 32, and his wife Ruby, 29, have been preparing meals for themselves and their living room because the housing management failed to fix their gas stove after it broke down last month, Marrow said.

He said he stopped paying the $80-a-month rent in February because a portion of their kitchen ceiling that fell in November was never fixed.

The maintenance problems are so masssive "we can't keep up with them," Moore acknowledged in an interview. "The place is just getting worse."

One other public housing project already is slated for a complete overhaul before the five-year, $18.2 millon program announced by Barry yesterday.

The James Creek dwellings, a 267-unit project in Southwest, received a $7.1 million grant from HUD two years ago. No work has begun and none is expected until spring, Moore said.

Most of the two years, he said, have been consumed with meeting two HUD requirements -- formulating a get-tough policy against tenant vandalism and nonpayment of rent and submitting a plan for refunding to the city treasury some $19 million that the public housing authority overspent in the last 10 years.