Fuel pressure sensor displaying unusual fluctuations.
Are you seeing large pressure fluctuations while logging the fuel pressure?
this could be why
The Ford Mustang from 2018 onwards have 2 fuel pressure sensors. one sensor is in the “low side” fuel rail for the port injectors and the other is in the “high side” for the direct injector fuel rails.
Even on an unmodified Mustang the fuel pressure can be observed as unusual.
There are a couple of reasons for this.
- The low side fuel pressure sensor is mounted in the fuel rail right along side of the fuel injectors so every time a fuel injector opens and closes it will cause small pressure pulses in the fuel rail and the sensor will then send that information to the PCM. On a modified vehicle with larger fuel injectors the pulses can be even larger. Non OEM rails could also possibly contribute.
- Using an OBD scanner to data log the fuel pressure can be misleading depending on the program being used. The sample rate can often be adjusted. For example HP tuners scanner can display as fast as 10ms which is reasonably fast.
What to do next
The first step is to confirm the sensor’s accuracy. Use a suitable mechanical fuel pressure gauge and check the fuel pressure before it enters the fuel rail. Check it under the same conditions as when the readings were in question.
If unusual fluctuations are not apparent with mechanical gauge. consider relocating the sensor away from the fuel rail if its having an affect on the operation of the engine.
If there is no effect on engine operation then it can be left alone.
