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Does anyone know what the fuel pressure is supposed to be on a 2007 Commander with a 4.7? Hooked up a gauge and got 55 with the key on engine off. When I started it, the needle was jumping rapidly between 55 and 65 psi. Is that high?
 

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Does anyone know what the fuel pressure is supposed to be on a 2007 Commander with a 4.7? Hooked up a gauge and got 55 with the key on engine off. When I started it, the needle was jumping rapidly between 55 and 65 psi. Is that high?
@Nyc2nc82; From the service manual;

The correct fuel pressure for this vehicle is 58 psi +/- 2 psi.

Sounds like you're about right.

 

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Discussion Starter #3
Thank you
So when I start the engine is the pressure supposed to stay steady? Mine was jumping up and down. I have a video of the gauge, not sure if I’m able to post it
 

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Thank you
So when I start the engine is the pressure supposed to stay steady? Mine was jumping up and down. I have a video of the gauge, not sure if I’m able to post it
I would assume it's supposed to be steady - but I'm not 100% certain.

Are you getting any DTC's that makes you believe something is wrong?
 

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Discussion Starter #5
Have been having issues with some rough running on and off. You replied to me on my thread about the misfires. The overall problem has improved but still getting some misfires and hiccups while driving. It seems to be worst when it’s hot out. Running the AC seems to make it happen more. It also seemed to get worse the less gas I have in the tank. I was below half the other day and had some issues. I decided to fill up and it seemed to get better. Decided to get a gauge and test the pressure. Most other videos I have seen the gauge seems to stay steady when idling but can’t find anything for this vehicle specific
 

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Discussion Starter #6
Have done a bunch of stuff so far and trying to narrow it down. Was thinking maybe injectors or fuel pump next
 

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Discussion Starter #7
I did change the MAP sensor last night too. It seemed to drive great but it was at night and not as hot. Didn’t run the AC either.
 

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I did. Took it to the dealership. Feel like I was robbed. All they wanted to do was a seafoam cleaning and wanted to charge me almost $300 for it. Have my own scanner. Main codes have been p0305 and p0300. Already changed plugs, coils, did the seafoam treatment. Changed throttle position sensor, MAP sensor. Did a compression test, about 150 all around. So trying to see what I can tackle next. Thinking injectors since I am getting a single cylinder as well as the 300 but the way the gauge was jumping at idle not 100% sure of maybe the pump or pressure regulator which I believe is part of the fuel pump for this model correct?
 

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I did. Took it to the dealership. Feel like I was robbed. All they wanted to do was a seafoam cleaning and wanted to charge me almost $300 for it. Have my own scanner. Main codes have been p0305 and p0300. Already changed plugs, coils, did the seafoam treatment. Changed throttle position sensor, MAP sensor. Did a compression test, about 150 all around. So trying to see what I can tackle next. Thinking injectors since I am getting a single cylinder as well as the 300 but the way the gauge was jumping at idle not 100% sure of maybe the pump or pressure regulator which I believe is part of the fuel pump for this model correct?
I'm no mechanic; From what I'm seeing in the service manual, there is a fuel pump sending unit & a fuel pump module - which I'm pretty certain is the fuel pump itself.

I haven't seen any mention of a fuel pressure regulator.

I've also noticed that the service manual makes mention of making sure to relieve all of the pressure from the fuel system if you plan on removing the fuel pump; Even when the engine is not running, the fuel system remains under high pressure.

It also recommends draining the fuel tank.
 
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