Fuel rail pressure fault.

[mk420thae]

Been dealing with misfire faults for awhile now. After carbon cleaning, spark plugs, ignition coils and a fuel injector. Ended up breaking one of the arms for the runners, went with JHM and got the flaps tuned out. Removed the vacuum actuators and zip tied the flaps open. Now I've been getting a fuel rail pressure to low fault sporadically. And I've noticed in higher rpm high load like trying to pass on the highway without downshifting the car will hesitate real bad. No fuel leaks, that was my first thought, Didn't know when the fuel filter was replaced so did that last night. No change. About to do fuel pressure tests but wanted to see if anyone has seen sensors fail or the pumps. Hoping it's just the in tank pump.

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[mk420thae]

Low side fuel pressure spec is around 6 bar. When the car is acting up low side pressure is fine.

High side pressure spec is 18 to 120 bar.
When it's acting up its around 20bar at high rpm.
During a normal pull when it acts fine high side it around 60+ bar..


Sounds like a high pressure pump issue.. Right?

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[JimmyBones]

Yep. I think that your high pressure pumps are dieing. The good news I'd that high pressure fuel pumps have come down in price but the bad news is that you need two of them.

[mk420thae]

Yeah I was thinking the same thing... Just not a common failure.

I can get the pair for 500 from my dealership..


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[JimmyBones]

Yeah I was thinking the same thing... Just not a common failure.

I can get the pair for 500 from my dealership..


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Not as rare as you might think. I have seen it with RS4s, low revving 4.2 FSI engines (like Q7s, facelifted D3 A8s, and B8 S5 coupes), and the V10 S6/S8.

At least the V8s and bigger engines have a camshaft follower with a roller so that the camshaft follower is never an issue. Pretty sure that the V6s do too but I haven't taken one off in a while. Unlike the 2.0T FSI engine in the B7 A4s and Mk2 A3s/TTs that have a flat tappet style camshaft follower.