Fuel Pressure Regulator

[BArkward]

Hey everyone! I have a 2007 Audi A4 Quattro 2.0T. Keep getting codes P008B and P089 (fuel pressure regulator). I’ve already replaced the fuel filter and I replaced the fuel pressure sensor (on the fuel rail) just today. Code remains. Assuming the regulator is next but can’t find any info on where it’s located or how to replace, or even which exact part I need. Would be grateful for any help!

[Jay-Bee]

Fuel pressure is regulated in the low range by the fuel filter then by the high pressure fuel pump and the fuel rail valve.

Have you removed your HPFP and checked the cam follower? Might need someone with VCDS to do a bit of logging and see when and where it's dipping.

[Brillo]

Fuel pressure is regulated in the low range by the fuel filter then by the high pressure fuel pump and the fuel rail valve.

Have you removed your HPFP and checked the cam follower? Might need someone with VCDS to do a bit of logging and see when and where it's dipping.

Not the whole answer. The solenoid valve attached to the HPFP (N276) controls the pressure of the high pressure side of the fuel system. Rail fuel pressure info is sent to the ECU by the pressure sensor on the fuel rail. The ECU then (based on the tune) sends a signal to the N276 pressure regulating solenoid (valve on the HPFP) which controls the amount of fuel entering the HPFP from the low pressure side (based on demand). If you cannot achieve the called for pressure it is likely that the N276 solenoid on the HPFP is faulty.

IIRC, for a stock tune the high side max pressure is limited to somewhere around 110 to 115 bar. The pressure relief valve which is a simple spring-ball mechanical valve (on the fuel rail) controls overpressure of the rail by dumping excess fuel back to the low pressure side. I think that the relief valve is set to something like 130 bar. Aftermarket tunes may call for higher pressure (eg. 150 bar) in which case the pressure relief valve needs to be changed for one that opens at a higher pressure. Confusingly, this valve is often called the fuel pressure regulating valve. The short links below explains that part of my answer.

https://www.youtube.com/watch?v=Tq0yjpje-TQ

https://www.ecstuning.com/b-genuine-...AaAiIEEALw_wcB

[Jayz691]

Isn't that what Jay-Bee just said? Anyway, max rail pressure on stock tune is 109.9bar. The factory prv is 116(early model, BPG) and 126bar(late model, BWT).

But as mentioned, log you fuel pressures, blocks 230, 231 with vcds. Do some pulls to get it to act up, and look at the logs. See if low side pressure is dropping with the high side, or not. That'll give ya an idea where to start. If ya don't have vcds or something to log with, fuel issues can get expensive to fix by just guessing and part swapping..

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[Brillo]

Isn't that what Jay-Bee just said? Anyway, max rail pressure on stock tune is 109.9bar. The factory prv is 116(early model, BPG) and 126bar(late model, BWT).

But as mentioned, log you fuel pressures, blocks 230, 231 with vcds. Do some pulls to get it to act up, and look at the logs. See if low side pressure is dropping with the high side, or not. That'll give ya an idea where to start. If ya don't have vcds or something to log with, fuel issues can get expensive to fix by just guessing and part swapping..

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Yes Jay-Bee said that but his answer was a bit vague for a tyro, and added some additional info for clarity.

[Theiceman]

All good info here by everyone. It's great not having to know everything about every system on a car, there is always people who have great knowledge in different areas.

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