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I could not find this on the search menu. Does anyone have a diagram or video showing the workings of the Mk6 High Pressure Fuel Pump? I want to understand this potential problem. I found the older fuel pumps, but would like to see how the new one works.

Thanks,

Frog.
 

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PM sent. I haven't found any videos online. There are some pics of the internals here. http://www.myturbodiesel.com/forum/f7/dweisels-hpfp-analogy-failure-4187/

Basically, the pump shaft is driven by the timing belt. The pump shaft has a cam on it which translates the rotating motion into a back and forth motion. A piston rides on the cam and moves back and forth which is what moves the fuel. The fuel moves into the high pressure fuel rail, aka common rail. There's a pressure release valve which controls how much fuel can leave the rail. Because it is mostly restricted so that most of the fuel can't leave the rail, it gets pressurized. Then the injectors open and let the fuel into the engine.

There are 3 pumps. Electric lift pump in the fuel tank, a boost pump before the hpfp, and the hpfp. There are also a number of inline filters, even at the fuel injector.

On early VW gasoline direct injection engines, the fuel pump cam was driven by the camshaft. Those had problems wearing down and people thought that a roller would fix it. The TDI hpfp has a roller but on damaged pumps you can see wear on it. Some people think it's related to the bore, some people think that the piston can spin in place which means the roller is no longer riding on the cam which grinds it away. Some people think North American fuel is to blame because it's lower quality. It's all speculation at this time.
 
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