How to Troubleshoot a Mercedes Diesel

1. Check to see if the engine starts normally. On some older Mercedes diesels, the vehicle would not start or would have a tough time starting in extremely cold climates like those found typically in the northern United States and Canada. To correct this problem, you'll need to take your vehicle to a Mercedes dealership so that they can install a block heater. The block heater will keep the engine block warm, which will in turn make it easier to start on a cold day.
2. Listen for a rough idle when the engine warms up. Some drivers forget that they need to make sure that they are running diesel fuel and not regular gasoline in their diesel engines, and so they may have 1/2 tank of diesel fuel already and decide to fill up the tank, but forget to use diesel fuel (or assume that mixing fuels is OK). The high octane gasoline found at every gas station simply will not cause an efficient combustion in a diesel engine. In some cases, the vehicle will not start or run at all. You'll need to have the fuel tank drained for you by an experienced mechanic so that the tank can be refilled with diesel fuel.
3. Check to make sure that the Mercedes engine revs normally throughout the RPM range of your vehicle. The Mercedes diesel engines depend heavily on compression to make the engine work properly. Low or uneven compression in the Mercedes diesel engine can hinder performance, and prevent the engine from revving up. If this happens, you'll need to have the vehicle serviced by a Mercedes dealership.