Code P0191

Tiny
SAXYBILL1
  • MEMBER
  • 2007 FORD EXPLORER
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 105,000 MILES
Received code, replaced MAF sensor, fuel pressure sensor and fuel pump. After engine warmed up, cannot start. Have to wait twenty minutes before it will start again.
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Sunday, January 22nd, 2017 AT 7:08 AM

6 Replies

Tiny
HMAC300
  • EXPERT
Check fuel pressure with a gauge auto parts rent it, see link.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
for code 191 is fuel pressure sensor. see picture for causes. make sure you have quarter tank of fuel in-tank.
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Sunday, January 22nd, 2017 AT 8:44 AM
Tiny
STEVE W.
  • EXPERT
Did changing the parts eliminate the code? And then it will not start when warm? Or do you still have the code?
Why did you replace the MAF?
When it will not start do you hear the pump still prime?
Does it shut down once warm or can you drive it a while. Shut it off and it will not re-start?
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Sunday, January 22nd, 2017 AT 9:18 AM
Tiny
SAXYBILL1
  • MEMBER
Changing the parts did not eliminate the code, still have p0191. Yes, it will not start when warm. Replaced MAF because initial code was p0113. Yes, the pump primes. Yes, I can drive it for a while. However, when I shut it off it will not start for a while.
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Sunday, January 22nd, 2017 AT 10:17 AM
Tiny
HMAC300
  • EXPERT
Just becaue you hear the pump prime it may not be enough pressure to work do as I said in first reply
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Sunday, January 22nd, 2017 AT 12:56 PM
Tiny
SAXYBILL1
  • MEMBER
My response was to Steve W. Who asked if I could hear the pump prime.
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Sunday, January 22nd, 2017 AT 1:44 PM
Tiny
STEVE W.
  • EXPERT
From the description it seems the system is not holding pressure when shut off, that could be a bad check valve in the pump assembly.

A pressure test would show you that, Just connect the gauge to the port. Start the engine and let it run a minute or so. Shut it off and if the pressure drops real fast you have a bad check valve.

But that will not cause a P0191 code.
P0191 is set when the ECM sees a pressure lower than 20 psi or higher than 70 psi.
I believe the problem in this case is either the voltage or ground to the pump control module or the module itself.

Here is a nice video showing this system and some diagnostics. Much easier than typing it all out.
https://www.youtube.com/watch?v=gC0O1J4Am7E
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Monday, January 23rd, 2017 AT 9:43 AM

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