A high-pressure direct injection fuel pump can vary the pressure to the injectors from around 300 to 5,000 psi. So, how does it do it? This is the job of this electric solenoid on the side of the unit that controls the pressure and the volume of fuel.
During the inflow sequence of the cycle, the plunger or piston travels downwards. The control solenoid opens, and fuel enters the high-pressure side of the pump. The next part of the sequence is called the “spill” process or cycle. This happens when the piston or plunger starts to travel upwards, the control solenoid remains open for a specific period that is measured in milliseconds. Some of the fuel will spill back into the low side or supply side of the pump. The longer the control solenoid stays open, less pressure will be generated. A shorter open period will create more pressure.
For the system and solenoid to work as intended, the ECM needs to know the position of the camshafts and crankshaft to determine when the control solenoid will open. Why is this important to technicians? Simple. If you are diagnosing a fuel-related “crank/no start” or “limp mode” condition, the ECM must receive accurate information on engine position for the direct-fuel injection system to work. The direct fuel injection system might not work as intended if there are codes for the camshaft or crankshaft position sensors.
This video is sponsored by Carter Fuel Systems.