Low rail pressure, 3.0 CR-TDI (Solution)

Hello,

I'm having a problem with my Audi Q7, 3.0 TDI engine, engine code CASA. After a complete overhaul, including replacing the fuel tank, all 6 fuel injectors, pumps, and lines – everything related to the fuel supply – all components were replaced.

Now, according to the tester, I have the following error messages: "Fuel rail system pressure too low," "No communication," and "Fuel rail system pressure too low, mechanical fault."

Has anyone else experienced this?

Thank you very much.

Well, perhaps you should provide a little more information about the reason for this rather extensive repair.

We assume that everything has been properly installed, all lines are sealed, the fuel system is filled, and air can be bled out.

Then it's possible that the exchange happened because...

Okay, so now it's just a matter of guesswork, because there could be a faulty CR pump, contamination in the system, problems with the pre-injection pump, etc.

Hello, thank you for the reply. The high-pressure pump had a lot of debris in it, even though it was always filled with the correct fuel. The car has 187,000 kilometers on it.

Try resetting the control valve adjustment.

According to Audi, an SVM code must be installed in order to reset the values of the control valve.

If the rail pressure values are fluctuating wildly, it could be that the rail pressure sensor is faulty, the control valves are stuck or defective, or the high-pressure pump is failing. Cable problems could also theoretically be a factor, although I'm unsure whether this is practically possible without an error code like a short circuit to ground or positive.

I would start by checking the wiring harness while the engine is running. You could try gently tapping on the suspected components and see if it affects the engine's performance or the rail pressure.
Then check for fuel supply issues, and finally, look for shavings (in the diesel filter or the valves mentioned). And if nothing can be found, try replacing the control valves or the sensor, or use a measuring device to check what the actual rail pressure is.

Best regards, Rainer.

Hi Rainer, he had to take it to an Audi garage. For your information, the Q7: Generation 1 SVM code is 01a069, and the A4-A5-A6-A7 Generation 1 SVM code is 01a043. Everything is okay now. Thank you very much!

Thank you for your feedback .