Help Please Audi A4 2.0 TDI 170 Fuel Pressure Regulator Replacement


Registered User
so last week the car starts idling badly, exactly like the one in this video

so i have ordered the replacement off ebay, and also ordered a VCDS cable and software to try.

has anyone done this before? any pitfalls or things to watch out for. i am a bit worried by replacing this regulator that i will end up with air in the system.

i presume disconnecting the battery is wise or pulling the fuse on the fuel pressure pump ?

not having any youtube or haynes manual doesn't help!

any support really appreciated.


Registered User
It's quite a straight forward job. I would recommend removing the fuel rail to get full access. Once you reconnect everything, I would prime the fuel system using vcds. No need to disconnect the battery. If I get chance I will dig out some photos.


Registered User
I’d really appreciate that , i have ordered Vcds cable and will download vcds lite , hoping that has the fuel priming facility available . I plan to have a go this weekend all being well


Registered User
I have found some photos, I have made a quick guide that will hopefully give you a few pointers on how to replace your fuel pressure regulator.

1. Cut tie wraps to get access to the fuel rail, there should be about 2 of these.

2. Disconnect the fuel sensor at the front of the rail.

3. Disconnect your glow plugs and pull out your connectors.

4. Undo and remove the fuel line that runs from the HP fuel pump to the fuel rail, there a series of torx screws that keep the line in place, remove the line.

5. Unscrew your fuel lines that run towards the injectors, be careful with these as they are delicate.

6. Remove the pipe for the fuel return from the fuel rail, this can be a bit stiff so you may need a bit of WD40 to help release it.

7. Remove the two bolts that hold the fuel rail.

Once you have done this should give you access to the fuel rail. I would suggest putting the rail in the vice so you can remove the regulator. You will need a large spanner (I think a 30/32mm) to loosen it. I would also keep an eye on the orientation of the regulator on the rail, so when you place the fuel rail back in the engine bay it will sit correctly.

Follow the above steps in reverse.

Once you have reconnected everything. I would prime the fuel system using VCDS and then start the car as normal.



Registered User
Wow thank you so much for the write up. Very comprehensive and looks fairly straightforward . I am trying to get connected to the car before I actually replace the part , my vcds cable I bought seems faulty so I’m waiting on another one .i want to see if vcds shows the pressure dropping or not when idling . I have been looking at the MAF possibly as well, may try give that a clean before i mess with the pressure reg as that looks fairly straight forward too and would make sense in how it failed perhaps it has some **** that managed to get in it when I was on the motorway.


bobby singh

VCDS Map User
Gold Supporter
Remove the metering unit from the hpfp and checking for metal shavings inside. If you have metal inside then time for a new pump, injectors and flush through all the hard lines.

I have CP3 kits in stock for these which is far better pump and does not suffer from issues like the stock CP4.
Please note the cp3 pump calibration is not straight forward its not something every tuner can do.



Registered User
I have found some photos, I have made a quick guide that will hopefully give you a few pointers on how to replace your fuel pressure regulator.

Thank you very much for this write up. Very detailed.
I have a rough idle issue on my 2010 A4 B8 CAGA 2.0 tdi, which developed 3-4 weeks ago. Fine starting 1st time every time - doesn't die, no power loss - fine under load, normal driving, motorway driving, up hill etc, just at the traffic lights... it sounds like a diesel tractor with a hunting idle.

My issue looks and sounds very much like this guys car in this video:

I had my car in an indy VAG specialict shop to test the fuel system etc, all came back normal, they were scratching their heads as to what it could be and said the next step would be to replace HP pump and injectors (not necessarily in that order) and that they couldn't guarantee it would solve the problem.
The CP4 HP pump was replaced within 10K ago anyway so isn't old.
Since I don't have unlimited funds burning a hole in my pocket during this time, I am doing some of the fault finding myself.

I have ordered the spare OEM Bosch PRV, got a good deal from Ebay - and will be fitting this today. Thanks again for your write up.
I'm keeping my fingers crossed.


Registered User
as per my other post on the other thread. I replaced the PRV and the sensor on the fuel rail. It has solved my rough idling problem. Thanks for your help!