2002 Chevrolet Impala electrical system problems

Tl* the contact owns a 2002 chevrolet impala. The contact stated that there was oil leaking from the vehicle. On one occasion while driving, there was a odor of burning oil and then suddenly there was a fire near the engine. The front passenger was able to extinguish the flames under the hood. The driver, the front passenger and rear child passenger inhaled smoke due to the fire that affected their breathing.

I put a new fuel pressure sensor in and now my 02 impala wont start and not getting any power to fuel pump now, we are a car lot and this car has been sitting unable to start now for over 2 weeks, had many certified mechanics from our area observe the problem, including 2 certified chevrolet mechanics, and none have come up with a solution. Just don't make sense, I am sure chevrolet is aware of the problem so please let me know what the problem is so I can have it repaired so we can sell the car.