For the second time in a week the House rebuffed the Reagan administration on the dairy price-support issue yesterday, only this time it was worse.

As its dairy cost-cutting plan was rejected by a larger margin than the first time 'round, the administration's seemingly well-oiled lobbying engine appeared to be running out of fuel.

One White House official privately blamed the Department of Agriculture for letting things get out of hand. Secretary John R. Block was on a trade mission in the Orient. Two last-minute appeals by Budget Director David A. Stockman were ignored by House Republicans.

A week ago, as the House debated its new four-year farm bill, the administration's plan for reducing dairy price supports was defeated by 90 votes.

This time, notwithstanding Stockman's pleas and a ghost-written letter from Block to GOP leader Robert H. Michel (R-Ill.) seeking help, the margin was 102 votes and the administration's prestige was badly tattered.

Another clear indication in yesterday's vote was that the traditional farm coalition, warped and fissured in the Senate, had mended itself back together--at least long enough to uphold a middle-ground Agriculture Committee plan for dairy farmers.

The House plan would achieve savings identical to those in the administration approach during the current fiscal year. But over the life of the bill, it is estimated to cost some $500 million more, an amount the White House has deemed unacceptable.

Stockman traveled to Capitol Hill twice this week to urge Republicans to join forces against the committee's compromise measure. On Tuesday, according to reports, committee Republicans refused to heed his pleas. Yesterday, the GOP caucus gave him scarcely more help, although Minority Whip Trent Lott (R-Miss.) switched his vote to support the White House.

One of the White House's overnight allies, liberal Rep. Barney Frank (D-Mass.), reflected on yesterday's House scene, which at times took on the air of a Keystone Kops comedy.

"The administration is just in a shambles. They have a terrible time making tough decisions. They have a terrible time being consistent," Frank said. "They just made no effort to work their troops at all."

USDA lobbyists scurried about the corridors, seeking votes and urging that their floor champion, Rep. Paul Findley (R-Ill.), demand a roll call on his ill-starred amendment.

Arguments in the debate were identical to those used last week on the House floor--so monotonously familiar, in fact, that Rep. John G. Fary (D-Ill.) slept through much of the back-and-forth in a front-row seat.

After nearly two hours of debate on the Findley amendment it was shouted down to defeat with an anticlimactic thud. Findley was outside the chamber, providing an inquiring reporter with figures on how much his proposal would save.

The roll-call vote which went against him, 255 to 153, was made possible only after Findley hurriedly came up with another, nearly identical amendment that could be brought to a record vote.

Frank and Findley had led last week's effort to win passage of the administration's dairy program, the same approach already adopted by the Senate.

The House is slated to continue work on the bill today.