The back 3 injectors on 7m Toyota dont work?

I have a Toyota 7m engine and i have a problem with my injectors. I have got spark from my distributor and the spark continues to the sparkplugs but there is no combustion on the rear three cylinders. I know this because when the car is idling i can remove spark cables from distributor and there is no change in how the motor idles. Cables 4,5,6 are the ones i can remove. I have tried switching the impulse wires as well as the power to the injectors but it still doesn't work..Can anybody help?