# Fuel pressure at fuel rail?



## morey_b (Dec 2, 2015)

I'm trouble shooting a P0171 (lean) code on my 2007 Jetta and haven't located any vacuum leaks. I'm now looking at the fuel system. I haven't been able to track down a fuel pressure that should be shown at the fuel rail. Can anyone help me out. I'm showing about 26psi while running. I did change the fuel filter with no change in my lean condition. Thanks


----------



## morey_b (Dec 2, 2015)

Nobody have any clue what the normal pressure is?


----------



## halbwissen (Jul 20, 2001)

I'll check the Bentley for you tomorrow afternoon and report back.


----------



## morey_b (Dec 2, 2015)

Great. Thanks.


----------



## halbwissen (Jul 20, 2001)

Ok, so the Bentley instructs you to check fuel pressure at the filter fuel, not on the rail. According to the manual, the rail is only used to bleed the system. Fuel pressure at the filter should be 4.0-bar/58-psi at idle with a residual pressure of 3-bar/43-psi when the car is off.


----------



## morey_b (Dec 2, 2015)

Thank you for the response. When you say "at the fuel filter" you mean on the fuel pump side of the filter or after the filter? I'm going to have to rig up something to check the pressure there as all I have is the Schrader valve connection on my pressure gauge. Would be a lot simpler to give us a pressure at the fuel rail where we can connect up easily. 

I think I'm going to replace the fuel pump and see if that changes my lean reading.


----------



## halbwissen (Jul 20, 2001)

I'll take a picture of the page in the Bentley for you tomorrow.


----------



## halbwissen (Jul 20, 2001)




----------



## morey_b (Dec 2, 2015)

Thanks for that info man. I'm going to have to make up a rig to check it just after the filter. I would imagine that it should be the same pressure just after the filter as it would be on the fuel rail though. And mine only shows about 25 psi. I did just change the filter with a 4.0 bar filter/pressure regulator without a change is the lean symptoms. 

Would a bad fuel pump cause a lower pressure? Or do they either work or they don't?


----------



## morey_b (Dec 2, 2015)

So I checked the fuel pressure right after the filter and it's the same 25 psi or thereabouts at idle. So this is definitely lower than it should be. I changed the filter on my Nissan truck and checked that to make sure my gauge was accurate and the numbers were spot on, so it's not the gauge. 
The only thing I can think of is the fuel pump. Will be ordering a replacement soon.


----------



## morey_b (Dec 2, 2015)




----------



## Master_P (Feb 10, 2012)

Curious that the FPR is down by the fuel filter. I would expect it to be plumbed with the IM and therefore be located on the fuel rail.

Is it possible that the FPR is not working correctly? It's supposed to retain fuel pressure by restricting flow back to the tank. If too much fuel is getting back to the tank, the pressure at the rail will drop.


----------



## morey_b (Dec 2, 2015)

It is my understanding that the filter has a built in pressure regulator. I believe it is supposed to be 4bar.


----------



## morey_b (Dec 2, 2015)

Well today I received the second replacement fuel pump from HighFlow Fuel.com and both have arrived damaged. 


http://www.highflowfuel.com/i-21278...ta-gls-glx-vr6-wolfsburg-turbo-1999-2013.html










Does anyone know where to find a similar replacement under $100? I'm done with this company and want to find a different product.


----------



## morey_b (Dec 2, 2015)

The company sent me a third pump, this time the packaging was overkill and it made it to me in one piece. I installed it and took it for a test drive. 

My fuel trims are back to being right at "0" and the car is driving noticeably better. Glad I finally figured out my low fuel pressure issues.


----------

