An eyewitness to the fiery Ford pinto crash in which three teen-age girls died in August 1978 testified today that the car exploded "like a large napalm bomb" when it was hit from behind by a van.

Ford Motor Co. is charged with three counts of reckless homicide in the first criminal prosecution of a manufacturer in a products defects case.

Alfred J. Clark was one of six eyewitnesses called to the stand in the second day of testimony.

Each recalled that the Pinto exploded and was immediately engulfed in flames. Three witnesses testified that the car exploded a second time.

William J. Martin said he left his car, approached the wreckage and looked in the Pinto's windshield. "I saw a solid mass of orange flame. There was no air space in the passenger compartment" he said.

Clark also said he could see no one inside the subcompact, just "a fireball." Two of the victims burned to death in the car. The driver died of burns a few hours later at hospital.

Since Ford has acknowledged that burns were the cause of death, the court has not allowed any evidence describing the girls before or after the accident.As prosectuor Michael Cosentino complained earlier this week, "We can't prove anything about the victims themselves, and the victims are what this case is all about."

The prosecution had hoped to show through photographs, eyewitness accounts and testimony from medical experts that the victims did not die from any traumatic injury from the force of the crash, but from burns, inflicted when the Pinto's fuel tank ruptured, leaked and exploded.

Attorneys for both sides keyed on the issue of closing speed in the accident.

Clark said his first impression was that the collision would be a "fender-bender. The force of the impact was not that terrific." He said he heard no noise from the impact.

The 49-year-old retired carpenter, who said he suffers from severe heart trouble, was visibly disturbed in recounting the accident, and paused several times to calm himself.

He estimated the speed of the Pinto at impact to be 30 to 33 mph and the van's speed at 40 to 45 mph. But under cross-examination by Ford chief counsel James Neal, Clark admitted that he "wasn't driving their vehicles" and could not be "exactly" sure of their speeds.

Two witnesses said the Pinto had emergency flashers on. Yolanda Ihrig testified that the car was slowing to about 30 to 35 mph when she passed it just before the accident near Goshen, Ind.

Important to the state's case were assertions by all the witnesses that the Pinto was moving when it was hit. Estimates of the van's speed ranged from 40 to 55 mph.

In earlier statements, Neal had suggested that the Pinto was stopped when it was struck.

Neal has contended that the closing speed -- how much faster the van was traveling than the Pinto -- was 50 miles an hour and that any subcompact, and some larger cars, would have burned after such an impact.