I am helping my buddy on his 92 Mustang 5.0L. We bought it from an auction and had the ignition replaced.

Now when we try to start the car, the fuel pump will not come on & the injectors are not pulsing. Checked violated at the pump and we are getting around 3Volts. Checked voltage at the switch in the trunk and have 12volts. We tested the pump by putting 12volts directly to it and it works but not when we try to start the car. We replaced the relay on the passenger side under the hood & still nothing. We did a lot of research and ran a few test but still come up short. All Help is appreciated.

edit:

The car will start if we spray starting fluid into the throttle body. (I only did it to see if we was getting fire.)

 

Just to clarify, do you mean your loosing your voltage somewhere between the inertia switch in the trunk and the pump? Do you have 12V before and after the inertia switch ?

 

I'm pretty sure I had 12volts to both sides of it. I will double check again to make sure.

 

if you only have 3v at the pump while the pump is running(or trying to) then i would suspect high resistance in the wiring from the inertia switch to the pump. you could try jumping the wire from the switch to the pump and see if it runs then, if so overlaying that portion of the circuit is recommended