Fairfax County hasn’t found enough money to help pay for one of the Metro stations on the second part of the new Silver Line — a move that means the county and the other players will have to help pay for more of the roughly $3 billion price tag.

The county’s troubles with financing the station come as the testing of the Silver Line continues to have problems. For the second time in a month, a test train had issues, as it hit part of a fence near a platform on the first part of the Silver Line. The rail line, which is now under construction from East Falls Church to Wiehle Avenue in Reston, is expected to open early next year

On the second phase of the Silver Line, Fairfax had promised it would try to find private partners to help pay for the Route 28/Innovation Station. The station is expected to cost nearly $90 million, according to Fairfax officials.

But so far Fairfax has been unable to find a partner for the station.

The Northern Virginia Transportation Authority has promised $41 million to help pay for the Route 28 station and Fairfax has applied for a $20 million federal grant. Tthat leaves the station about $48 million shy of what it is expected to cost to build it. Fairfax has until July 1, 2014, officials theresaid, to find more money to pay for the station.

“We’ll continue to look for ways to fund that gap,” said Tom Biesiadny, director of Fairfax Department of Transportation. “We said we would use our best efforts and our best efforts means just about anything we can come up with.”

As part of a deal negotiated by former U.S. Transportation Secretary Ray LaHood, Fairfax had agreed that if it couldn’t find a partner to pay for the Route 28 station, they and the other funding partners — Loudoun County, the Metropolitan Washington Airports Authority (MWAA) and the federal government -- would pay for the station, as part of the project’s overall cost.

Under a complicated funding agreement for the second phase of the rail line, Fairfax puts in 16.1 percent of the total cost, while Loudoun puts in 4.8 percent, MWAA puts in 4.1 percent and users of the Dulles Toll Road will pay 54 percent. The federal government is expected to put in millions of dollars in loans but the amounts have not been set.

MWAA officials said Fairfax’s difficulty to find a partner won’t change the overall expected price tag of phase 2 of the project, which is now estimated to be $3.126 billion.

The Silver Line is being built in two parts at a cost of nearly $6 billion and is one of the largest transportation projects in the country. Construction on the second phase of the Silver Line, which will run from Reston to Dulles Airport, is expected to start in the spring of 2014.

As part of the LaHood deal, Fairfax and Loudoun County had also agreed to find private partners to help pay for five parking garages — two in Fairfax and three in Loudoun.

Fairfax has done a public-private partnership in helping build the parking garage at the Wiehle Avenue station, which is the last stop on phase one of the rail line.

Housing developer Comstock is building housing development there and Fairfax is paying to build the Metro parking garage at the Wiehle Avenue stop. To pay for the Metro garage, Fairfax said it will use lease payments from Comstock and parking garage revenues.

Pat Nowakowski, executive director for MWAA of the Silver Line project, said it was easier to find a developer “like they did at Wiehle Avenue” to agree to a development deal because of its location. But getting a developer interested in helping pay to build the Route 28 stop, which sits in the middle of the toll road to Dulles Airport, is a tough sale.

At Route 28, he said, “it is in the middle of a highway.”

“It was much harder for them to find a way to help cover those costs.”

Michael Curto, MWAA chairman, said he did not believe the additional expense would mean a toll increase.

“I don’t think any of this is problematic in the end,” he said.