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Mercedes MBE Changing Injectors

changing injectors on mercedes mbe

Replacing Fuel Injectors – Mercedes MBE 900 Diesel Engine

The video points out that the injectors are not meeting the required specs. The diagnostic software allows us to test the injectors for balance. The idle speed balance test shows how much extra fuel or less fuel the injectors are using. In other words the engine computer tries to add or take away fuel to each injector to make it run at it’s maximum potential. If the injector is plugged the engine computer will feed more fuel and the reverse if the injector is over fuelling.

The CTV Engine Brake

The engine brake is called a “constant throttle valve” (CTV). It consists of a piston and lip seal (works with engine oil pressure) which is secured by the injector hold down and easy to replace while changing injectors. It would be unwise not to replace the CTV pistons and seals which are not a high cost. It takes so much disassembly time to get to these components it would be a shame to go through the whole process again if the CTV system failed.

Case In Point “Low Doser Code”

On another Mercedes engine in our fleet there was a low doser fuel pressure code. I covered this problem in depth on a previous post. The Detroit troubleshooting procedures for this engine is excellent and can be found on their website under “power service literature”. The first step was to check fuel pressure which feeds the unit pumps (supplies each injector with high pressure fuel) and supplies pressure fuel to the doser block which feeds doser injection and runs the DPF regeneration process.

Once we replaced the two valves that control fuel pressure in the return fuel system they raised the back pressure increasing fuel pressure from 55 psi to 71 psi so this fixed the regen code and also added more engine power. The driver reported a 15 to 20 km increase when on a steep grade. The hours we spent testing the fuel system paid off and we’re more than prepared for any fault code in the future.

The Future of Mercedes MBE 900 Engines

The Mercedes MBE 900 is a popular engine in our shop right now for engine and emission codes along with this low power condition that has led to a complete injector replacement. This model is not available any more but I have been assured by the dealer that the parts will be there when we need them. I’m relieved because these engines are going to be in our fleet for at least another 6 years. Thanks for reading this and take a couple of minutes to leave a comment.