Code P0191

MICHEL PETRIN

MEMBER
2004 FORD E-SERIES VAN
6.8L
V10
2WD
AUTOMATIC
100,000 MILES

I have a code P019, but the 'check engine' is not lighted.
I changed the rail fuel pressure sensor (3 times).
I changed the fuel filter.
I changed the fuel pump control module.
I installed a gauge in line before the filter, and the pressure with the key on but the engine not running is 20PSI. The pressure with the engine running is between 38-40PSI.
The pressure in line decrease to almost zero in 24 hours.
The Snap On 'computer' told us that the sensor pressure signal is about 47PSI while running.
As soon as I erased the error code, I came back almost instantly.

I do not know if I have to change the pump or not.
Since the 'check engine' is not lighted. Is it an important problem or not?

5 Replies

MASTER ASE TECH

MEMBER
82 POSTS

Hi,

I'm Dan. It appears that your fuel pressure key on, engine off, is below spec and points to a fuel pump replacement. I've attached a Ford TSB to help you with this code. Follow the steps in the attached document and you should be ok. Let us know what you find.

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Friday, November 12th, 2021 AT 1:56 PM

MICHEL PETRIN

MEMBER
3 POSTS

Thanks just did the test and I have 4.21k Ohms on it.

Still one more question.
Where is the fuel pressure temperature sensor? I know where is the pressure sensor but no idea about the temperature sensor.
Is the pressure sensor is also used for temperature?

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Friday, November 12th, 2021 AT 2:54 PM

KASEKENNY

MECHANIC
18,907 POSTS

That is correct. The fuel pressure and temperature sensors are included on the same sensor if it is equipped that way.

The wiring diagram for this engine shows that you have an injection pressure sensor and then a separate Fuel tank pressure sensor.

I attached those below.

However, it looks like your pressure sensor is ok as it is within the specified range.

So that means we need to re-evaluate why you only have 20 PSI when you turn the key on.

Based on what you have done, I suspect the pump is the issue. So even following through the testing that Dan posted earlier, if you turn the key on and don't get a minimum of 35 PSI then you need to check the wiring to the fuel pump and if is ok you need to replace the pump.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Based on the fact that the PSI is correct when the engine is running, I suspect the wiring is fine, but you just have a pump that is starting to fail.

I attached this info below and let us know what you find. Thanks

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Monday, November 15th, 2021 AT 4:00 PM

MICHEL PETRIN

MEMBER
3 POSTS

I want to do a follow up of my situation. I tried to remove the pump from inside my RV making an access door. But I broke two studs, so I had to take the fifty gallons of gasoline out and lower the fifty-five gallons tank. I repaired the studs and put a new pump.
This morning, I filled the tank and turn the key without starting the motor.
Now the pressure is near 50 PSI (at my first trial). Before it was close to 20 PSI.
The code P0191 is no more present, and the motor still run great.
Like you wrote, my pump was falling.

I just want to thank everybody who tried to help me.

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Friday, November 19th, 2021 AT 11:47 AM

KASEKENNY

MECHANIC
18,907 POSTS

That is great that you got it figured out. Plus, we really appreciate you coming back and providing that detail as it will surely help others.

Please come back in the future if you have other questions. Thanks