T4 AXG Pump: Troubleshooting & Adjustment

Hello,



I'm having a problem with the diagnostic check.



I have two identical T4 2.5 TDI vans with the AXG engine, both manufactured in 2002. I'll call one "Bus D" and the other "Bus E".



Zu Bus E: Wenn ich mit VCDS rein gehe zur Dynamischen Pumpenprüfung kommt ein Warnton,die Vorglühlampe blinkt und das Motorgeräusch verändert sich hörbar. Auch Soll/Ist - Werte zeigt es an. SoweIt's all okay.



Regarding bus D: This bus exhibits poor cold start performance. When I use VCDS for a dynamic pump test, no warning sounds are triggered, the preheating lamp blinks, and the engine noise doesn't change. The displayed values are completely inconsistent.



My question: What changes inside the pump when the engine noise changes, as in the case of Bus E?



"With Bus D, no change in the fuel injection start time can be detected on the VCDS system, even though it has been altered. The fuel injection pump was replaced 5 months/5000 km ago and is a replacement unit. Since then, the cold start performance has been poor. After several hours of adjustment, the engine runs even worse than before."



My question: Is the pump's electronics faulty?



Over the next few days, the injection pump will be adjusted using a measuring device. Possibly the pump is defective (mechanical issue)?



Thank you.

Hi,

Please perform a VCDS scan of both buses first.

Best regards, Rainer.