Ford Repair: Mustang Wont start, powertrain control module, ford mustang

Question
1995 V6 Ford Mustang won't start, just cranks. There is a clicking noise coming from the Powertrain control module when the key is cranked or in the on position and the rpm gauge goes back and forth as it is cranking. I have replaced the PCM and the Engine control unit, but no luck. What could be wrong?

Answer
Unfortunately there are really too many things to list.Let's try checking the timing chain/belt.When was it last serviced.Two things to check for before you get back to me,(fuel and fire).Both are required of course and either will cause you're symptoms.Just to let you know,if you have fuel to the rail that doesn't always mean that you don't have a fuel problem.You would also need to check fuel pressure.Good luck and let me know what you find.