Consolidated Rail Corp. yesterday reported third-quarter net income of $120.2 million, a decline from the record profit of $140.8 million in the same quarter last year.

The drop was due in part to the fact that utilities and other coal users were not stockpiling coal this year in anticipation of a coal miners' strike, as they were last year.

Nonetheless, this was the third straight quarter in which Conrail's earnings trailed the same quarter a year earlier and will doubtless be used by the administration to buttress its argument that Conrail's long-term prospects are limited and that the federally owned railroad should be sold to Norfolk Southern Corp. to guarantee its financial stability.

For the first nine months, Conrail reported earnings of $329.7 million, compared with $410.6 million for the same period in 1984. However, Conrail was not paying full rail industry wage rates until July 1, 1984. It says that an "apples to apples" number would be $345 million for the first nine months of 1984.

The earnings report came the same day that a group calling itself the Conrail Minority Stockholders Association asked Sen. John C. Danforth (R-Mo.) to withdraw his Senate Commerce Committee's legislation approving the sale to Norfolk Southern.

The group consists of Conrail employes, who own the 15 percent of Conrail stock not held by the federal government. "We, as employes, view Conrail's viability as our own and we are prepared to do whatever necessary to that end," the letter to Danforth said. "We ask the Congress for the same chance given to Lockheed and Chrysler," two publicly held corporations that received significant federal survival assistance.

The letter also cited antitrust concerns about a Norfolk Southern-Conrail merger. Similar concerns will be expressed in House Judiciary subcommittee hearings today by representatives of several state governments in the Norfolk Southern-Conrail territory.

Conrail Chairman L. Stanley Crane said that despite the fact the railroad's freight carloadings are down 8 percent for the latest nine months from the same period last year, "Conrail was able to reduce operating expenses in the third quarter and first nine months and produce solid results from railroad operations."