2005 mustang high fuel pressure problem. - Ford Mustang Forum
 
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post #1 of 9 (permalink) Old 01-03-2014 Thread Starter
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2005 mustang high fuel pressure problem.

Anyone out there have this problem. Check engine light on as well. Code p0191. I cleared the codes several times , then replaced the fuel rail pressure sensor on top of fuel rail. The reading on scanner went back to normal range running 39 to 43 psi.after one day the same code came back on p0191. Fuel pressure on scanner shows 79+.Now I am thinking maybe something wrong with the fuel pump or relief valve. Or maybe something else. Any help much appreciated.

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post #2 of 9 (permalink) Old 01-03-2014
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It seems rather odd that a new sensor would show normal pressure for only its first day. Can you install a mechanical gauge in the line and verify what the actual pressure is? That would help to diagnose a possible electrical problem between the sensor and the gauge.


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post #3 of 9 (permalink) Old 01-03-2014 Thread Starter
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Thanks for your reply. I was thinking that maybe there is an electrical fault. Good idea I will check pressure. Is there a special adaptor I need , and would it plug into the fuel pressure rail somewhere..? Not sure as it does not have a return line. Another thing I noticed is that the pump is noisey when key is turned on and it does not cycle off at any point, it just runs all the time. Thanks for any further input.
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post #4 of 9 (permalink) Old 01-03-2014
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The pump should not be noisy. But if it is I don't see how that would boost pressure, but I could see how it would be reduced. And it should be on all the time with the ignition. The pump is always on and the relief valve bleeds out excess fuel and controls the pressure in the system.

Maybe the pressure relief is clogged, causing the pump to work hard and it's worn out. That was my first thought, but the initial reading from your new sensor points to an electrical problem.

I don't know what kind of adapter you'll need for a mechanical gauge. Measure the hose going to the rail and discuss it with your local parts supplier. Like any plumbing problem.

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post #5 of 9 (permalink) Old 01-03-2014 Thread Starter
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Thanks for that. It is making a little bit more sense now. So the pump running is normal all the time. I think you are right that maybe the relief valve may be stuck. Is it part of the pump itself...? Still I will check fuel pressure to determine if electrical reading is the same.
Does the tank have to come out to access fuel pump or is there access through the floor somewhere..?
I will try and get a picture of where everything is....thanks again for your input.
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post #6 of 9 (permalink) Old 01-04-2014
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Best to reference your Haynes or shop manual for specifics.

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post #7 of 9 (permalink) Old 01-13-2014 Thread Starter
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OK.. I changed fuel filter and no difference. I changed the fuel pump with a new OEM ford pump. It had a superceded part #. And then hooked up mechanical fuel pressure gauge in line. Koeo it pumps 90 psi and when car is running it is 95psi. When you turn off pump it sits at 50 psi. Check engine light stays on when running. Same code p0191.
Next I think I have to do electrical checks. Maybe another sensor is tied in with the frps. First I will check all grounds at pcm and I am getting some electrical contact grease to put on all connectors. Any other ideas to try will be much appreciated.
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post #8 of 9 (permalink) Old 01-15-2014
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I had the same problem on my 2008 GT. It was the Fuel Rail Pressure Sensor. I changed that out and cleard the code with my tuner and all is great so far.
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post #9 of 9 (permalink) Old 01-22-2014 Thread Starter
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Updating what has happened with the check engine light and fuel pressure problem.. I went to radio shack and got a can of contact cleaner with grease . I pulled the bolts on 4 ground wires under the hood and every engine harness connector and sprayed this stuff on and reconnected. Also I did the 3 main connectors on pcm. Also did the fuel pump and pump controller by spare tire..
MAGIC....... the problem has gone. No more high pressure or engine codes. Fuel pressure now is 39 to 44 psi. I drove the car on a road trip to San Fran.. no problems.
Unfortunately..I don't know what fixed the problem as I did everything all at once. But I am very happy.
Thank you for all your comments and help...
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