The fuel pressure sensor relays the fuel pressure back to the ECU to control the fuel pump with PWM and keep a constant pressure over the injectors. This is important for the ECU to supply an accurate amount of fuel per engine stroke. The ECU can vary the speed of the fuel pump to increase or decrease fuel pressure accordingly. The sensor gives a continual feedback of fuel rail pressure so that the ECU can make pressure adjustments almost instantaneously. This setup allows the engine to run without a manual fuel pressure regulator or return line. The 4 Bar Map sensor, 5.5 Bar DP sensor, or 7 Bar Map sensor can be used as a fuel pressure sensor. The setting differs for each of them and is discussed in the software.

Operation

The Pressure Sensor requires 5 volts DC which is supplied to sensor by the ECU. It then generates a signal from 0 to 5 volt equivalent to the pressure range of the sensor.

Sensor Location

The fuel pressure sensor must be mounted inside the engine bay. The pressure input pipe must be securely connected to the high pressure fuel line with a T piece. The sensor must be mounted higher than the fuel line with the pressure nipple facing downwards. This will produce an air bubble between the sensor and the fuel to prevent damage. The fuel does not actually contact the sensor element and the bubble acts as a damper to the pulsing fuel. The other pipe of the DP sensor must be connected to the intake manifold. It could be joined with the MAP sensor line if the takeoff pipe has a large enough hole to prevent delays in the signal.

Pressure sensor types

The fuel pressure sensor available from Spitronics is the Motorola series sensor
The fuel pressure sensor is rated at 5.5 bar differential pressure (DP) and the aluminum one is 4 or 7 Bar MAP.

Sample Sensor Pinout and layout