By HELGA SILVA

For the last four weeks Gaspar Jimenez has been sitting in a Mexico City jail. Authorities say he is involved in an international kidnapping and. murder scandal. His family sits at home, baffled at the news.

Jimenez, 40, is an unskilled laborer who worked overtime for the Florida East Coast Railway so he could add a swimming pool to his three-bedroom house. He took a second job last Christmas to buy a stereo system for his young daughters.

"We rarely were seen together because my husband didn't like parties, the movies, visits or socializing," his wife said. "He rarely left the house other than to go to work. All he did after work when he got home was watch TV."

His cellmate is Orestes Ruiz Hernandez, 28, a high school dropout from Hialeah, who, according to his father, worked his way up from a refrigeration technician to become the owner of his own refrigeration repair firm.

Jimenez, of 5250 SW 2nd St., and Ruiz are accused of attempting to kidnap the Cuban consul of Merida, Mexico, and killing the consulate's chief of investigations on July 24.

Jimenez was shot in his left arm by a policeman accidentally during his arrest.

A third man, Gustavo Castillo, managed to elude the Mexican police and is believed in the United States. The FBI, which became involved in the case at the request of Mexican authorities, is looking for Castillo and trying to determine whether there was a Miami-based conspiracy to attack another country.

It was the third attempt against Cuban embassies in less than a year. A fourth, almost identical, occurred last week when two Cuban Embassy officials were kidnapped in Argentina.

The families of Jimenez and Ruiz - who did not know each other before the incident - have pooled their resources to hire a lawyer for the two men.

"I was shocked when I read the news in the papers," said Mrs. Jimenez. "He was not involved or active in any political organizations that I know of."

Ruiz' father, Mario Ruiz, was also worried. "We have always been a very close family and he has always been responsible in his business and never discussed or even talked politics at home," said the elder Ruiz. However, Ruiz and his wife moved to Puerto Rico last year and had lost touch of the day-to-day activities of their son who remained in Miami.

Friends agreed that Jimenez, a naturalized American citizen, was a quiet, reserved man. He was a freight handler "who was always on time, a good worker who rarely missed a day," according to his foreman, Orlando Manrique.

However, he did have strong political convictions. He fought against the Batista regime as a guerrilla in the famous ninth column under Huber Matos in Cuba..

When Matos fell out of grace with Castro and was jailed in October 1959, Jimenez was jailed with the group. After his release he renounced his military commission with the rebel army and left the island in March, 1961.

Ruiz, who has retained his refugee status, came to the United States from Cuba in 1962 with his parents when he was 14. He had no political affiliation known to his father or his clients.

Jimenez allegedly went to Mexico to recuperate from a gastric ulcer operation.. "He had never taken a break in all the 15 years we have been in the U.S. All he had ever done was work like a mule," said Mrs. Jimenez, a teacher's aide in the Dade Public School system.

He worked until noon of the day he left for Mexico - July 19. He did not tell his boss that he was leaving, nor did he take vacation. "After several days missing from work someone called us and said he was in New York with a sick brother," said Manrique. "After the news and all the days missing he was automatically dropped from the company.

At work his friends raised $200 to help the family defray expenses.

No one knows why Ruiz went to Mexico. His father has not been allowed to talk to him since he was arrested.

Mrs. Jimenez flew to Mexico city July 27 and spoke with officials at the U.S. embassy, but did not attempt to visit her husband in jail.

"The Embassy didn't dissuade me, but I felt insecure in the area and I had to think about my two children back here," said Mrs. Jimenez. "However, they (U.S. officials) have seen him and they say he is okay but looks very tired."

Ruiz, who was caught at the Merida Airport in Mexico with a false passport issued to a "Manuel Allen," cannot benefit from any U.S. Embassy services abroad since he is a refugee.

"He is stateless," said a spokesman for the State Department's Special Consular Services. "Terrorist activities are against U.S. policies and the U.S. cannot appear involved in the case of terrorism against a third country which we are not at war."