The Seaboard Coast Line Railroad cut off credit to Auto-Train Corp. yesterday, canceling its long-term contract with the financially troubled railroad that hauls tourists and their cars between suburban Lorton and Florida.

Auto-Train is more than $4 million behind in payments to the Seaboard for use of its tracks, and its checks have been bouncing since July, the SCL said. From now on, Auto-Train will be allowed to ride the Seaboard's rails only if it pays cash in advance, the railroad notified the Interstate Commerce Commission.

Auto-Train Chairman Eugene K. Garfield said later in the day that a $19,500 check was delivered to the Seaboard, so the next Auto-Train can leave for Florida on schedule at 4 p.m. today.

"The train will run. I'll be there personally to see it off," said Garfield, who two weeks ago assured Auto-Train stockholders that "this company will survive," despite financial problems that have pushed it to the brink of bankruptcy.

Two other creditors -- the Internal Revenue Service and the Richmond, Fredericksburg & Potomac Railroad -- also put pressure on Auto-Train yesterday.

Richard Shumate, president of the RF&P, said his railroad will "have to take the same position" as the Seaboard unless Auto-Train pays $422,000 it owes for use of its tracks.

The IRS, which last month filed a $1.6 million lien against Auto-Train for failing to pay the government taxes withheld from employes' checks, yesterday slapped the company with another lien for $525,000. Besides the $2.1 million covered by the liens, Auto-Train "is not current" in making other tax payments, the company disclosed.

Auto-Train said it plans "to make a substantial payment to the IRS" as soon as it gets the money from a $3.7 million loan recently negotiated with a Swiss bank. Those funds could be available today, Garfield said.

Even with the Swiss loan, Auto-Train still needs additional financing to continue operating, Garfield said. The company is seeking a government-guaranteed loan from the Federal Railroad Administration and is trying to sell stock in a newly formed subsidiary that builds and repairs rail cars.

"We need two out of the three," Garfield said yesterday. On a day-to-day basis the railroad is making a profit, he added, but not enough money to repay its debts, most of which are overdue.

Besides the $4 million Auto-Train owes the Seaboard for use of its tracks, Seaboard has guaranteed another $2 million of Auto-Train's debts and could be liable for that amount if Auto-Train can't pay.

The Seaboard "has been patient in the extreme" and "has made major concessions time after time to assist At [Auto-Train] in avoiding financial and operational collapse," SCL attorney Clifford Losh said in a letter notifying the ICC it is terminating its agreement with Auto-Train.

A Seaboard spokesman said the company finally decided to cancel the agreement because Auto-Train has not "been able to develop an approach that we deem feasible" for paying its bills.

Garfield insisted that the Seaboard's termination of its agreement with Auto-Train was a "technicality."

"This is really a change in the payment plan," said Garfield. "It's an attempt to set up a toll booth on the tracks and put us on a pay-as-you-go basis."

Garfield said Auto-Train lawyers believe the Seaboard cannot legally cancel the operating agreement without prior approval of the ICC.

"While the company is in default on several other obligations, none of the other creditors has indicated any intent to take further action at this time," he said in a statement issued late in the day.

But some other creditors already have taken steps to see that they will be first in line for their money if Auto-Train goes out of business. If other creditors demand cash payments or file lawsuits for their money, Auto-Train's financial troubles could worsen quickly.

Until now, the creditors have continued to give Auto-Train more time to pay, apparently fearing that if they demand their money, others will, too. Several major Auto-Train suppliers, including Marriot Corp., not only have extended credit to the railroad but also helped it out by in effect co-signing Auto-Train's debts.

Privately, Auto-Train executives complained that the Seaboard's action was "a dirty trick" designed to assure that the Seaboard gets as much as possible of the money Auto-Train is borrowing from the Swiss bank.

RF&P President Shumate said "it was strictly a business decision" to stop extending credit to Auto-Train. He said Auto-Train is overdue on more than $400,000 in payments for use of its tracks between the Auto-Train terminal in Lorton and the Seaboard Coast lines at Richmond. The RF&P has guaranteed $600,000 of an Auto-Train loan from the Paul Revere Life Insurance Co. and could have to pay if Auto-Train cannot.

Continental Illinois National Bank of Chicago, which owns Auto-Train's locomotives, has sued to repossess the engines because the railroad is behind on lease payments. A hearing on that case is scheduled next week in Chicago. o

Auto-Train also has been sued by the ICC for defying its order to set up a special bank account to give refunds to customers in case the railraod goes out of business.

Auto-Train has collected more than $2 million on advance ticket sales, and the ICC wants it to put $500,000 into an account to protect the customers. The ICC has been trying for months to make Auto-Train repay another $500,000 to customers who canceled their Auto-Train reservations but have not been given their money back..