2016 Peterbilt 579 PACCAR MX-13 Low Fuel Pressure SPN 94 FMI 18

Question

I am getting a recurring derate and a yellow MIL on my dash while climbing grades. My diagnostic tool is showing SPN 94 FMI 18 which indicates fuel delivery pressure is lower than expected. The truck feels like it is starving for fuel under heavy load but idles perfectly fine.

torque_terry · Accepted Answer

The issue turned out to be a failing Fuel Pressure Sensor (Part #2042405) located on the fuel module. Even though the filters were new, the sensor was skewed high at idle and low under load. I replaced the sensor, cleaned the electrical connector with contact cleaner, and the fuel pressure now stays steady at 11.5 bar under full torque. The part was about $180 and took 30 minutes to swap out.

Jake Morrison · Answer

Hook up a manual gauge to the diagnostic port on the fuel module. If the manual gauge matches the sensor reading, your lift pump might be getting weak or the screen in the tank is restricted.

Jordan Lee · Answer

Check your fuel lines for any signs of collapse or air bubbles. PACCARs are notorious for the quick-connect fittings sucking air on the suction side without showing an external leak.

Lina Brooks · Answer

You should check the fuel pressure relief valve on the fuel rail. If that valve is leaking internally, it will return too much fuel to the tank and you won't maintain the 10-12 bar required under load.

2016 Peterbilt 579 PACCAR MX-13 Low Fuel Pressure SPN 94 FMI 18

Suggest a repair