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Old 05-24-2011, 02:40 PM   #1
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08+ Returnless Fuel System

I'm curious to know how in the world the 08+ fuel system works. There is no fuel rail pressure sensor on the 08+. I thought that sensor was the heart of the returnless fuel system. The sensor allows the ECU to calculate the pressure drop across the injectors, correct? So, if that sensor is not there, how is the ECU calculate the pressure drop across the injectors?

150whp/135lbs-tq @ 13lbs.
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Old 05-24-2011, 07:43 PM   #2
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Interesting ...

Here is what I found for the 2007 and older Duratec:

Verified by a pic of a 2005 Focus Duratec engine:

The 2008+ does not have the sensor, as you said:


My thought right now is the sensor was simply moved. I notice the newer cars have an added heatshield on the firewall. Maybe it's back there?

It is possible that they don't have one at all. If you know the duty cycle and flow of the pump as well as the injector duty cycle and flow you can figure out the theoretical fuel rail pressure. The older ECU's did this already. Maybe Ford engineers got enough data they where able to build a flow/pressure map that was perfect, nixing the need for the sensor. But having a redundancy in the system would of been a good idea IMO.
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Do it correct, or do it twice.
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Old 05-25-2011, 10:36 AM   #3
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Also what I want to know is how there is no "fuel filter" on my 2009.
It's just a screen. Supposed to be lifetime durability.
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Old 05-25-2011, 10:55 AM   #4
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Originally Posted by tetra View Post
Also what I want to know is how there is no "fuel filter" on my 2009.
It's just a screen. Supposed to be lifetime durability.
I believe the filters are inside the fuel pump and it is a lifetime filter. the fuel was always filtered twiced anyway going through the sock on the fuel pump then the filter outside the fuel tank.
Don't have a Focus at the moment...Working on fixing that problem.
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Old 05-25-2011, 12:30 PM   #5
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There is no sensor to measure the psi drop across Inj its basicly all dont in the fuel pump assy and they carry much higher fuel psi 56-58 psi

I have never had the chance to have a fuel pump assy out to look it over but guessing there is an inline psi regulator built in

Correct the filter is the sock filter on the fuel pump , kinda silly to have 2 filters

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Old 06-15-2011, 01:05 AM   #6
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I belive tom to be correct. the sensor is in the fuel pump assembly
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