2007 explorer with p0191, replaced the maf sensor, fuel pressure regulator sensor and fuel pump. Engine light on and after warm up, difficult to start until a half hour later

Asked by Jan 20, 2017 at 06:34 AM about the 2007 Ford Explorer Eddie Bauer

Question type: Maintenance & Repair

6 Answers


Maybe a faulty injector? Wiring? Check the voltage to the fuel pressure sensor first.


Also, I know it's a (very) long shot, but maybe try the purge valve, maybe it's stuck?


Also a long shot, check the PCV/breather hose. Does your dipstick pop-out? (indicating high crankcase pressure?)


P0191 FORD - Fuel Rail Pressure Sensor Circuit Range/Performance... Possible causes; Low or no fuel, Faulty Rail Pressure (FRP), Sensor FRP harness is open or shorted, FRP circuit poor electrical connection, Faulty Fuel Pump...... Engine will not start P0191 FORD Description The FRP sensor is a diaphragm strain gauge device. The FRP sensor measures the pressure difference between the fuel rail and atmospheric pressure. The FRP sensor nominal output varies between 0.5 and 4.5 volts, with 0.5 volts corresponding to 0 MPa (0 psi) gauge and 4.5 volts corresponding to 26 MPa (3771 psi) gauge. The sensor can read vacuums and may lower the output voltage to slightly below 0.5 volts. This condition is normal and is usually the case after several hours of cold soak before the vehicle dome light is turned on. The FP module is energized at the same time the dome light is commanded on. A disabled or malfunctioning dome light does not affect the FP module control. The FRP sensor is located on the fuel rail, and provides a feedback signal to indicate the fuel rail pressure to the Powertrain Control Module (PCM). The PCM uses the FRP signal to command the correct injector timing and pulse width for correct fuel delivery at all speed and load conditions. The FRP sensor, along with the fuel volume regulator (part of the fuel injection pump), form a closed loop fuel pressure control system. An electrically faulted FRP sensor results in the deactivation of the fuel injection pump. Fuel pressure to injectors is then provided only by the FP module. When the fuel injection pump is de-energized and the injectors are active, the fuel rail pressure is approximately 70 kPa (10 psi) lower than FP module pressure due to the pressure drop across the fuel injection pump. Thus, if the FP module pressure is 448 kPa (65 psi), then the fuel rail pressure would be approximately 379 kPa (55 psi) if the injectors are active.

So what are you suggesting I do?And please, in laymen terms. I am not a mechanic


Start by checking the fuel pressure. Not sure on this one but usually it is around 40 lbs. This would be checking the fuel pump and the fuel regulator. If the fuel pressure is not where it should be then a dead head test is performed to see if it is the fuel pump itself. All is good here then replace the Fuel Rail Pressure Sensor. You would need to make sure the wires are good at the plugin as they can break in the insulation. OR just take it in to be fixed.

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