Relative Fuel Pressure?
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Fleet Owner
Joined: Aug 2010
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From: Reynoldsburg, Ohio
Relative Fuel Pressure?
2005 E-350 with 5.4 engine, about 50K miles on the Ford reman'd engine. New intake & injectors, original fuel pump FPR etc, new fuel filter.
Just curious about a PID that's available on my rather modest OBD-II scanner concerning the PID for "relative fuel pressure". How reliable is that as an indication of the actual fuel pressure?
I'll be installing an actual fuel pressure gauge temporarily for testing but curious how that PID would be useful in the future?
TIA
Just curious about a PID that's available on my rather modest OBD-II scanner concerning the PID for "relative fuel pressure". How reliable is that as an indication of the actual fuel pressure?
I'll be installing an actual fuel pressure gauge temporarily for testing but curious how that PID would be useful in the future?
TIA
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
Assuming your scan tool is displaying the PID data from the FRP sensor, the following note from the PCED should apply:
Note: With the engine running, the FRP PID value may be 48-70 kPa (7-10 psi) higher than a fuel pressure reading taken with a mechanical gauge
Thread Starter
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Fleet Owner
Joined: Aug 2010
Posts: 21,255
Likes: 1,657
From: Reynoldsburg, Ohio
Okay updating my own thread! 
2005 E-350 extended body, 192K miles 5.4 gas engine with the mid-ship fuel tank, fuel pump does NOT have the accessory ports, Motorcraft # PFS-303. 192K miles. I wanted to check actual fuel pressure with an external gauge attached through the Schraeder fitting on the fuel rail----except on this van there isn't one I can find. There what appears to be an electronic sensor fitted on the passenger's side, where I'd expect to find the Schraeder fitting.
The throttle body and fuel filter have both been changed about 200 miles ago--failing throttle body.
SInce I don't have one what is the recommended procedure for pressure testing? Through my scanner I get just about 39.8 PSI at idle, moving upwards to 45 at freeway speeds (2000 RPM, 70 MPH). If I'm to assume an actual gauge pressure would be about 10 PSI higher that should be acceptable correct?
I suspect I'm having early symptoms of a fuel pump failure---without the Schraeder fitting I don't know how to test its operating pressure. No real issues apart from a "surging" when pulling a slight grade, no DTC's showing as of this moment. I can watch and graph the FRD PID in real time.
TIA
2005 E-350 extended body, 192K miles 5.4 gas engine with the mid-ship fuel tank, fuel pump does NOT have the accessory ports, Motorcraft # PFS-303. 192K miles. I wanted to check actual fuel pressure with an external gauge attached through the Schraeder fitting on the fuel rail----except on this van there isn't one I can find. There what appears to be an electronic sensor fitted on the passenger's side, where I'd expect to find the Schraeder fitting.
The throttle body and fuel filter have both been changed about 200 miles ago--failing throttle body.
SInce I don't have one what is the recommended procedure for pressure testing? Through my scanner I get just about 39.8 PSI at idle, moving upwards to 45 at freeway speeds (2000 RPM, 70 MPH). If I'm to assume an actual gauge pressure would be about 10 PSI higher that should be acceptable correct?
I suspect I'm having early symptoms of a fuel pump failure---without the Schraeder fitting I don't know how to test its operating pressure. No real issues apart from a "surging" when pulling a slight grade, no DTC's showing as of this moment. I can watch and graph the FRD PID in real time.
TIA
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
Yeah, electronic return-less fuel systems don't have the test valve. You have to either use an in-line adapter or a tee adapter at the FRP sensor in order to use the mechanical gauge. Sorry, don't have specs or details handy as I haven't had to research that.
FRP PID should show 28-45 psi while running.
FRP PID should show 28-45 psi while running.
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