I have a full auto start 750p and through the data box you just press the button for prime and the pump runs as long as you hold down on the button on the data box and I stop when I see the fuel reach the engine case.
I had the same problem with my 750p but it was a fuel solenoid problem, would only run on propane.
The EGT has to reach 200c b4 the fuel is introduced on my setup.

I use Alberto from Modelbau when I have problems or need service.