Having Mechanical Fuel Pump in the vehicle (kia classic) already , car is working fine , the flow of the fuel is actually perfect , but as soon I turn on the AC , the car's engine doesn't take much load and is suddenly switched off automatically , I just had a new engine installed , everything is new , new wiring , it is properly tuned, the only thing that I didn't change was fuel pump , so was wondering that could be a problem with it , may be the fuel pump producing the right pressure for the volume flow.