Gasoline Direct Injection (GDI) Vehicles are already showing up in service bays, so now is the time to develop the skills to quickly diagnose fuel
system issues. Below are four steps to help diagnose GDI Systems.
1. Connect an enhanced scan tool and selecet the data parameters for desired fuel pressure and actual fuel pressure.
2. Key On Engine Off (KOEO) the fuel pressure sensor should read low pressure pump pressure, approximately
50 to 75 psi. If the fuel pressure is below spcification, focus on the low pressure pump circuit and components.
3. Key On Engine Running (KOER) monitor the desired fuel pressure and actual fuel pressure data parameters.
The actual fuel pressure should be a close match to the deisred fuel pressure in all operating engines.
4. If the actual fuel pressure is too low or too high the pressure regulator data parameter
should be monitored for a higher or lower than normal value. This information will help determine if this
issue is related to the high pressure pump, low pressure pump or high pressure pump control circuit.
