Consumer prices rose a scant 0.2 percent in August, the fourth consecutive month at that level, indicating that 1985 could end up with the lowest inflation rate of any year since 1967, the Labor Department reported yesterday.

A bumper year for crops and continued weakening of energy prices promise to keep the consumer price index moderate, economists said. So far this year, the index has risen at an annual rate of 3.3 percent, compared with 4.0 percent for all of 1984, the Labor Department said.

If the rate holds at 3.3 percent for the year, it will be the lowest pace of inflation since 1967's 3 percent, the Labor Department said.

The effort by the United States and four of its allies to push down the value of the dollar probably will have little effect on prices here for at least 12 months, economists said. Generally, when the value of the dollar declines, imports become relatively more expensive compared with U.S. goods. As the prices of imports rise, domestic competitors also tend to raise their prices.

However, many economists said that foreign producers probably will push down their prices to maintain market share as the value of their goods in dollars increases.

White House spokesman Larry Speakes said the CPI report shows "we have a very stable price situation, both on the wholesale and retail levels." The report "speaks well for the economy," he said.

In a separate report, the Commerce Department said orders for big-ticket factory goods rose 3.4 percent in August, with all of the gains in the aircraft and defense industries. Excluding defense orders, the increase would have been 2.5 percent. Excluding aircraft orders, there would have been no improvement at all in orders for nondefense items.

Nondefense capital goods -- basically new machinery and construction equipment used to help industry expand and increase productivity -- rose 1.5 percent.

Orders in July fell a revised 2.3 percent, Commerce said.

The new orders report suggested that the economy will continue to grow in coming months at a moderate pace, dispelling fears of accelerating inflation brought on by rapid growth.

David Berson, a senior economist at Wharton Econometrics, said he expects the moderate inflation rate to continue. "Food prices should continue to be quite moderate," Berson said. "There are going to be bumper crops this fall that should, in fact, push food prices down. There is going to be some decline in energy prices. We're likely to see some more."

Berson said that in the next few months, price increases could slow to a 0.1 percent monthly rate. The consumer price index, excluding food and energy, increased at a 0.3 percent rate in the last six months, Berson said. "It's unlikely that will change very much in the last few months. We have not nor are we likely to see an acceleration of inflation in the next year."

Although many economists said the decline in the dollar probably would not lead to higher prices for some time, Roger Brinner, chief economist for Data Resources Inc., said that every 10 percent decline in the dollar would increase wholesale prices 2 percentage points and consumer prices 1 percentage point after a lag of about a year.

DRI forecasts that two years from now the dollar will be 20 percent lower than it is today, leading to a 3 percentage-point increase in wholesale prices in three years and consumer prices rising at a 4.5 percent annual rate, more than 1 point above the current rate.

According to the Labor Department, a dramatic slowdown in consumer prices began in late spring and continued through the summer. Between May and August, the department said, the price index increased at an annual rate of 2.5 percent, compared with 4.2 percent for the first four months of the year.

The deceleration in prices was largely the result of a drop in prices for used cars, energy and grocery-store foods, which all had price declines in the first four months of the year, Labor said.

However, during the May-through-August period, housing costs increased at an 8.1 percent annual rate, up from a 4.6 percent rate during the first four months. Shelter costs accounted for 70 percent of the increase in the overall index between May and August.

Food and beverage costs rose 0.1 percent in August for the third consecutive month. For the past 12 months, food prices have risen 1.7 percent. Grocery-store food prices declined 0.1 percent, reflecting decreases in the indexes for fruits and vegetables, meats, poultry, fish and eggs and dairy products. Beef prices have declined each month so far this year and were 7.7 percent below their level last December.

The transportation index declined 0.4 percent in August, the fourth consecutive monthly drop. Used-car and gasoline prices were largely responsible for the slowdown, Labor said. Gasoline prices declined 0.8 percent in August and were 12.1 percent below their peak level of March 1981.

Prices for new cars rose 0.4 percent, although the costs of automobile finance charges dropped 2.5 percent last month because of discounting of finance charges by major auto makers.

Although housing costs rose 0.5 percent following increases of 0.3 percent in both June and July, the cost of natural gas and fuel oil declined. Fuel oil costs last month were 17.1 percent below their peak level of April 1981, Labor said.

Telephone costs, however, increased 0.6 percent, Labor said.

The consumer price index last month was 323.5, which means that goods costing $10 in 1967 cost $32.35 in August.