LOS ANGELES, JUNE 24 -- Regulators probably won't find a buyer for troubled Financial Corp. of America, the nation's largest thrift, before Federal Home Loan Bank Board Chairman Edwin J. Gray leaves office next Tuesday, the head of FCA said today.

And if a deal isn't done by the end of the month, sources said, pressure to sell the thrift likely will lessen because of the heavy cost to the Federal Savings and Loan Insurance Corp., which itself is bankrupt and seeking an infusion of new capital from Congress.

President Reagan's nominee to replace Gray, M. Danny Wall, has taken no postion toward Irvine-based FCA, the parent of American Savings & Loan Association of Stockton, Calif.

FCA's chairman and chief executive, William Popejoy, said he believed from recent conversations with bank board officials that regulators have put efforts to find a buyer for FCA on hold.

"The great sense of urgency no longer seems to be there," Popejoy said.

Separately, the Wall Street Journal reported the bank board had asked the leading bidders to revise their offers to reduce the potential cost to the FSLIC.

The time needed to do that and to weigh any reworked bids could almost certainly preclude any deal before Gray left office, sources said in interviews. The sources spoke on condition of anonymity.

Gray has been pushing hard to find a buyer for FCA because he reportedly wanted to leave a clean slate when his successor took over.

But it has been estimated it could cost the FSLIC several hundred million dollars to sweeten any deal for a buyer, either by taking over some of FCA's $1.68 billion portfolio of bad loans and foreclosed property or by absorbing some of the company's future losses.

Of a half-dozen bids received by the bank board, those that received the most attention by regulators were from San Francisco-based First Nationwide Savings, a unit of Ford Motor Co., and from an investor group headed by former Treasury Secretary William Simon and former Federal Reserve Board vice chairman Preston Martin.

Both the Ford and Simon-Martin bid would inject $1 billion in capital into FCA, a minimum requirement the bank board made for all bidders.

For two years, FCA has received waivers from the bank board's Gray permitting it to operate below the required capital level.

The Ford and Simon proposals also would require FSLIC, which insures depositors for up to $100,000, to absorb some future FCA losses.

Spokesmen of the bank board, First Nationwide Savings and the Simon group declined comment.

Under Popejoy, who was installed at Gray's behest in late 1984 after the bank board forced the ouster of his predecessor, FCA has been healing itself slowly.

After losing $590.5 million in 1984, it posted profits of $53.2 million in 1985, $95.4 million in 1986 and $9.2 million in the first quarter of this year.

But FCA's huge portfolio of soured loans and foreclosed property continue to hinder its performance.