The fuel tank systems in the discontinued Chevrolet Vega cars are just as dangerous as the controversial systems used in the Ford Pinto, consumer advocate Ralph Nader charged yesterday.

Nader also charged that the proposed fix for the fuel tanks in the 1.5 million Pintos being recalled by Ford was "inadequate." Ford ordered the recall just days before government hearings were scheduled to begin into the charges that the Pinto was prone to catch fire in rear end collisions.

In a press conference yesterday with auto safety consultant Byron Bloch, Nader further contended that Ford had tested a safe fuel system for the Pinto as early as 1970 but deferred putting it into the 1973 model Pinto because federal regulations did not mandate the safeguards until later.

"The Pinto is not alone in its fuel tank vulnerability," said Nader when he made his charges about the Vega. The reason the controversy over unsafe gas tanks has so far centered on the Pinto, he said, was because Ford decided to fight lawsuits from crash victims, while General Motors chose instead to settle Vega lawsuits out of court.

Nader said the National Highway Traffic Safety Administration has begun to investigate the Vega. NHTSA administrator Joan Claybrook confirmed that GM had, in the past two days, dropped off a box of materials in response to NHTSA requests about the Vega fuel system.

GM spokesman Bill Noack said, "GM is cooperating fully with the NHTSA in its investigation of the Vega fuel system. We disagree with charges that the Vega fuel system is deficient. GM is confident that the integrity of the system will be vindicated."

Of the 1.9 million Vegas produced between 1971 and 1977, "we know of 14 that have been involved in rear impact crash fires involving injuries," Noack added. "In the 14 crashes, 13 persons died; five in one crash alone."

Noack said there had been seven lawsuits on the matter "and two are pending."

Bloch said the Vega is "fraught with the same problems as the Ford Pinto." He said that the gas tank of both cars is located at the rear of the car, and that the Vega particularly had a number of protruding objects near the tank that could cause a puncture if the car is in a rear-end accident - including one "Beer can opener" clamp that is used only to hold the car down on the transporter carrying it to the dealer.

But NHTSA crash data, obtained by The Washington Post, shows that Vegas did considerably better than Pintos in comparative crash tests, showing only slight leaks and no fires.