Common Rail Direct Injection (CRDI) – Delphi or Bosch depending on generation Bore x Stroke: 88 mm × 88.3 mm Compression Ratio: 18.0:1 (Standard) / 17.5:1 (EVO) Essential Sections of the Workshop Manual
Proper torque is critical for the aluminum components and high-pressure fuel system of the OM646. 90∘90 raised to the composed with power angle turn 90∘90 raised to the composed with power angle turn Main Bearings: Connecting Rods (Big End): Crankshaft Pulley (Harmonic Balancer): Injector Clamps: (always use new stretch bolts). 3. Maintenance Intervals & Fluids
The Bosch Common Rail system is precise. The manual provides guidelines for checking fuel pressure, replacing injectors (including cleaning the injector seats), and troubleshooting the high-pressure fuel pump. B. Turbocharger System
Align the mark on the crankshaft pulley with the timing pointer on the engine block. Mercedes Workshop Manual Om646 Engine
Without a manual: You remove the valve cover, see slack in the chain, and try to replace it. You don’t lock the camshafts, the crank moves, and when you start the engine, the pistons hit the valves.
Place a catch pan under the oil pan and remove the 13mm drain plug.
Indicates boost pressure is too low or too high. Inspect all rubber intercooler hoses for splits, check the intercooler core for cracks, and ensure the vacuum lines or electronic actuator controlling the turbocharger VNT vanes are operating correctly. Common Rail Direct Injection (CRDI) – Delphi or
While the timing chain is durable, it needs inspection. The manual includes the specialized procedure for aligning timing marks and replacing the chain tensioner to avoid catastrophic failure. 4. Common Problems Covered in the Manual
A workshop manual will guide you through all necessary maintenance. Here are some of the most critical procedures for the OM646 engine.
The OM646 is notorious for carbon buildup around the fuel injectors—a phenomenon known in the Mercedes community as the "Black Death." This is caused by a failure of the copper injector seal ring. Removal Steps Maintenance Intervals & Fluids The Bosch Common Rail
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Whether you are a professional mechanic or a dedicated DIY enthusiast, having access to a is essential for maintaining this diesel workhorse. 1. Introduction to the OM646 Engine