2009 diesel reluctant to start and does not respond to throttle

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B100
Posts: 7
Joined: Tue Jan 19, 2021 7:11 pm
Passat model: B6

2009 diesel reluctant to start and does not respond to throttle

Post by B100 »

This 2L engine has become difficult to start. Even when it does eventually start after lots of cranking, it only just runs and often cuts out. When the engine does run, there is no response from the throttle for 15-20 seconds. When there is finally a response, the revs increase slowly to about 1600rpm - at which point the engine springs into life and responds to the throttle. From then on and until the engine gets completely cold, it starts well, but lacks any pull below 1600rpm, making the car difficult to drive without stalling the engine.

Listen to it on Youtube https:/youtu.be/oddatga3hYE

I've been struggling with the engine for some weeks with no hint of what the problem is. There are no fault codes. New starter and battery fitted to speed up the cranking speed. Injectors have been professionally tested. All the glow plugs work. The fuel lift pump gives a good steady flow. The fuel filter has been changed. The intermediate fuel pump gives a powerful flow. The injector pump has been changed for a second-hand unit which has been dismantled and inspected, showing no signs of wear. The original injector pump also shows no signs of the usual CP4 cam and roller wear. The fuel rail pressure sensor has been changed. The fuel rail pressure regulator has been changed.

The fundamental question is about why this engine, when it does start, runs with very little power and fails to respond to the throttle. Any thoughts please ?
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