First, what do you mean by not starting? Will it crank?
Does the fuel pump prime? Can you hear the main relay click? I can see hearing the fuel pump a problem due to noise however the most cost-effective way is to hear for its distinct humming sound after switching the ignition on. Same applies for the main relay-if it ever stalls in the quiet of your home.
Also, I have seen bad ECU fuses do this occasionally, check into that. If corrosion is present on the terminals clean it with a salt and vinegar solution following by caustic soda solution.
Did you check the sensors for continuity? Don't spend your money on false guidance. Replace what needs replacement and you are affirmed about. It may cost you a penny after all to end the issues with just a little bit of insight.
As for wiring, have it soldered and heat shrinked for the better.