I just replaced my water pump, timing belt, thermostat and radiator in my 1990 lexus ls400 due to overheating problem. Drove it to oreillys just fine, let it run for a few minutes then turned it off. I then started it pulled out onto the main road and not even a minute later the car just shut off. I pulled over and tried to start it and it cranked up and turned over for about a second and just shut back off. Tried again and it started so I tried to drive it and it shut right back off 15 seconds later. Now everytime it just cranks, acts like it's turning over then shuts off. It was running fine after I had replaced everything so I know it's not the timing or spark plugs, need help please.