Diesel return valve

Hello!


I previously thought that for VP37 engines, the return valve is integrated into the diesel filter housing.
However, my 'How to Fix It Yourself' book states that it's temperature-dependent, meaning that the diesel either passes directly through or through the filter, depending on the temperature.


Where is the 'actual' diesel return valve then?

(This refers to the AEL 140PS R5 engine - if someone can describe an equivalent engine, for example, from the AFN range, that's also okay!)


Thank you and best regards,
Henrik.

Okay, the AEL is a bit different in that, as far as I know, it still has a water sensor in the diesel filter.

First, a counter-question: What is a "diesel return valve" in your understanding?

The component on the filter is the only valve in the fuel lines.
Depending on its temperature, the diesel either flows back from the pump to the filter to be re-filtered before returning to the pump (creating a short circuit, as is often forced in pool operation), or it flows directly back into the tank.

This design simultaneously enables the warming of the cold diesel fuel during start-up and idling (short circuit), and on the other hand, provides self-venting (when the return flow goes back to the tank).

m;

Thank you!


'No, I'm asking because I have the feeling that fuel is leaking out of the ESP overnight, and that's why the AEL always gurgles for 5 seconds after 8 hours of inactivity, and it sounds like it's not getting any fuel.'
That's why I thought the fuel might be flowing backward, and the pump needs to prime first. However, I don't see any bubbles at all in the transparent hose on the return side.


Does the ESP itself still have a valve?


Best regards, Henrik.

No, what other kind of valve could possibly be in the pump?

The transparent hose should be connected to the outlet (at least, that's how it is on the Golf).

The pump itself may still be leaking and drawing in air.

Let's stop for a moment and listen closely - my old G2 made a grinding noise, and it always took forever to crank before it would start again.

m;