GDI Petrol Engine FRP Sensor Output

Simon Diagnostician Clevedon, United Kingdom Posted   Latest   Edited  

Hi everyone, 

What reading would you expect from a fuel rail pressure sensor on a petrol GDI engine if the sensor was not in the rail but plugged in the connector loom?

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Brandon Diagnostician
Reading , Pennsylvania
Brandon Default
 

I imagine that is dependent upon how the circuit is engineered. The relationship between voltage and pressure

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Chris Technical Support Specialist
Commack, New York
Chris Default
   

maybe 0 psi

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Brandon Diagnostician
Reading , Pennsylvania
Brandon Default
 

If I am not mistaken… Those sensors are capable of displaying negative pressure as well. So, perhaps you are correct

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Simon Diagnostician
Clevedon, United Kingdom
Simon Default
 

This I what I would assume aswell but I had a friend that has a problem with a car and he said that scan data shows 390kpa when it's not even connected to the rail , he has tried 2 new sensors already and I have told him to check the power and ground and all ok and even the signal wire can be simulated and scan data will change, so I would say wiring integrity is all fine including the ECU, I

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Matt Technician
De Soto, Missouri
Matt Default
 

Some cars will show "default" values when it sees an issue with a sensor or wiring. Myself I'd be checking wiring from sensor to module by load testing them. Verifying they are good wires and can carry a load. If they are fine and he has tried 2 new sensors(it probably isn't the sensor then) then I would wonder about the module.

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Brandon Diagnostician
Reading , Pennsylvania
Brandon Default
 

Have you inquired about a “known-good” for comparison?

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Matt Technician
De Soto, Missouri
Matt Default
 

He doesn't even have a car listed, so we are just randomly guessing as to what might be seen. We really need some specifics.

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Steven Mechanic
Spokane, Washington
Steven Default
 

I've seen at least one that only went down to a specific pressure, not all the way down to zero. I don't remember exactly how low it went, but it was something like 5 Bar. I think it was on an Audi.

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Simon Diagnostician
Clevedon, United Kingdom
Simon Default
 

Again it's NOT my job it's a friends... all I know is that it's a 2006 Vauxhall vectra 2.2 gdi petrol and its had loads of parts thrown at it ,, the wiring has been checked and LOAD tested but sensor still reads 390kpa.... all I was asking (which people seem to overlook here) is would you expect to see a fuel rail pressure sensor reading anything when it's open to atmosphere??

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Simon: It would be understandable to see around 101kpa at sea level, on a clear day. Now, I've got a couple of question for you. How is your friend coming up with a 56.6psi (390kpa) reading at atmosphere? What is being used to measure this? A scan tool? What is the circuit voltage reading? Does it support the measure of 390 kpa? While you mention things have been checked, you appear to

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Wow, what you are overlooking is you have no idea, or at least have not told us, how the system is designed, what vehicle is being worked on and how you are measuring the sensor. Scan tool readings can be modified by the PCM, displaying a default value when an implausible value is seen by the PCM for example. Or only displaying a value between a set range. You ask a question that is

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Simon Diagnostician
Clevedon, United Kingdom
Simon Default
 

Thank you Eric and Anthony you have both answered my question i understand more now . Thanks again .

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Phillip Diagnostician
Anchorage, Alaska
Phillip Default
 

If you are having fuel pressure reading problems. It could be the high pressure pump.( I've only ever seen them just not work or have really low fuel pressure like 100 PSI or lower.) Or it could be the fuel pump. Example i had a Volvo come that was worked on by 2 other shops with a fuel pressure sensor code. What has happening is normally the fuel pump runs between 20-35% I believe, but was

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