Does anyone know how to test a Shut off valve on a 1999 turbo. I have replaced all the fuel lines and delivery valve o rings. I have also replaced the K40 relay but still no pumping. I can see that all the fuel lines are full of fuel and I can hear the SOV click when the key is turned.
I am interested in finding out if anyone else has had a SOV fail and what the symptoms were.
This car has been run on 100% biodiesel for the last four years. The problem developed a few months after returning to diesel fuel.

The car ran well before if failed to start. I did have a few time where it was hard to start and that is why I replaced the fuel lines.

 

If I don't have an error code on the OBD can I assume that it's probably not the fuel rack?
This car would loose power sometimes for a few seconds and was hard starting sometimes and all the search results I got all said it was the the fuel system or 40 relay.

 

I left the car parked all night with the back end jacked up with full tank. The next morning I cranked again for about 30 seconds and fuel started pumping out. What a relief.

Then I drove the car down the driveway and almost couldn't make it back. The transmission slipping like crazy. Error code 715 on OBD

I wonder how many people have sworn to never buy a Mercedes again after having one of these cars.