If this problem has been ongoing since you aquired the car. Try to establish if the injection pump has been replaced with a north american version. If it has the euro injection pump ignore this. Or if the problem started after you purchased the car.

Basically under certain circumstances people have eliminated the cigar hose. The euro pump equiped cars did not have one. So if the injection pump was replaced with a north american version you should install a cigar hose in the circuit.

What I have mentioned is an extremely rare stuation. The engine does tend to act differently at different fuel levels with out one present on the north american version sometimes.

Also these diesels are pretty straightforward. No computor and no ignition system involved. You have the basic engine and a fuel system. I am lazy I suppose but adding a fuel pressure gauge helps to eliminate possibilities quickly. Since you do not have a gauge installed.

Try closing the return from the injection pump off temporarily to see if there is a differance. No harm is done by this as the fuel or lift pump does not stall rather it just sits at a steady pressure determined by an internal spring. While your there have a look for air coming out the return with the fuel as well. No fuel coming out of the return? Your primary fuel pressure is too low.

Submerging a line in a little fuel and watching for air production as well in the fuel will let you know if the primer pump is good and that there are or are not points where air may be getting into the system. You do not have a stream of bubbles processing up through the small clear filter do you? One large pretty static bubble is normall in the small filter..I like simple tests. I dislike changing parts on simple speculation.


What can occur with a very very weak or open injection pump return relief valve. The level of fuel in the tank tends to affect the available pressure in the base of the injection pump. This is why closing the return line off is helping to establish if there is a problem there. . If there is no change at all with the return line closed and no air being processed in the jar test. Then the lift pump may be suspect. A permanently installed liquid dampened 0-30 pound gauge is a good way to monitor a fuel system like this.

It tells you many things but is most importantly giving an early warning when something is deteriourating. You are lucky in that the problem is fuel level dependant. That puts the issue squarely into the fuel system area. No subjectivity there.