Welcome.
We need more details.
Step 1 is install clear line inplace of the return line coming out of the ip (injection pump) to ensure no aeration or contamination in fuel and that fuel is flowing. It is 1/4” ID, about 5” long in an upside down “U” shape at the front, top portion of the ip. Clear oine available at any hardware store (but not rated as fuel line) fuelline.com that is good for permanent install, etc
Did you do that?
Second step is measure fuel pressure getting to ip. 8-14 is desired but anything above 1psi should allow it to idle properly. Maintaining 1psi while driving is required or it will starve for fuel and self aeration inside the ip will occur.
Before replacing the ip, replace the pmd with a KNOWN GOOD pmd. Note, they must be attached to a heat sink before powering up or instant damage can occur.
You said someone installed a pump. Guessing not water pump. Lift pump or injection pump was installed? Guessing ip because you mentioned shut off SENSOR?!!? There is no shut off sensor. There is an electric solenoid termed FSS (fuel shutoff solenoid).
If that is not getting power or is bad, fuel will not flow and engine will not start. Jumper power to the lift pump, key on, and observe if fuel is flowing through the clear line.
If you or anyone else installed a new or used ip- it will need to have timing set using a computer. But lets find out first what exactly you have.