ignition problem in Nisan Tsuru 8 valves

Hello

friends I need your help I have a tsuru 8 valves Red cover 1995 and 4 times to change the bomb in a year.
Ultia time I took it with the mechanic because I did not want to turn on. This I diagnose again gasoline bomb I bought it again and the car worked for a few hours and melted no longer what I turned on and I diagnose that the gasoline regulator was damaged did not get it anywhere, I bought another regulator of Nisan the mechanic I adapt it and the car worked perfectly for a few hours. I stopped at home after a while I wanted to light it and nothing. I already supply in the pump and marks me around 20 psi. I no longer know what to do would accept the suggestions that you want to give me !!!!