OM606 Injection Pump Throttle Lever and Fuel Pressure Setup Guide

OM606 injection pump throttle lever setup and fuel pressure management are two areas where small improvements make a big difference to drivability and reliability. Today we cover the correct throttle lever configuration and why static three bar fuel pressure is the complete solution.

The Injection Pump – Simple But Complicated

The Bosch M pump fitted to OM601 through OM606 engines is simultaneously one of the simplest and most complicated fuel delivery devices ever made. Think of a carburetor – it looks simple but sit down without one and try to design it from scratch. The complexity hidden inside that simple exterior is extraordinary.

The same applies to the injection pump. Experienced diesel pump shops with 30-40 years of rebuilding conventional pumps still cannot calibrate a performance super pump correctly. This is why only a handful of people worldwide can build these pumps properly. The elements, levers, helix angles and calibration interact in ways that take years of specific experience to understand.

Respect the pump. Buy from people who genuinely know how to build them. A pump element sitting unused in a drawer or installed in a pump that does not work represents money wasted on insufficient knowledge.

Treating the Pump as a Fuel Rail

As covered in previous videos the injection pump is the fuel rail of a diesel engine. Six hard lines exit the pump – one per cylinder. Fuel flows in, fuel returns. Treat it exactly like a petrol fuel rail.

Fuel system setup:

• Electric pump in line
• Pre-filter before the pump – check micron rating against pump manufacturer specifications, some pumps do not like high restriction pre-filters
• Fine filter after the pump and before the injection pump
• Return line from injection pump to fuel pressure regulator
• Regulator set to static three bar
• Return from regulator to tank
• Injector return completely separate back to tank

The injection pump itself is essentially indestructible. The elements inside are precision engineered components – treat them accordingly and they last indefinitely.

The Throttle Lever Problem

The stock rear throttle lever on the OM606 injection pump is adequate but has a fundamental weakness. The cable run is long. Long cables develop slack. Slack means imprecise throttle response – a slight delay between pedal input and pump response that worsens over time as the cable stretches.

Drive over a small bump and the cable moves slightly. The pump responds slightly. The car surges slightly. This is not a fuel system problem or an oil squirter problem – it is a cable slack problem.

The Correct Front Lever Solution

The injection pump shaft passes completely through the pump. The stock throttle lever is on the rear. The front of the shaft is accessible and can accept a second lever on the opposite side.

Installation process:

1. Set the pump to full throttle using the original rear lever
2. Fit the new front lever to the shaft in the horizontal position at full throttle
3. Tighten the front lever securely
4. The original rear lever can now be left in place or removed

Above the front lever position Mercedes placed two well-positioned intake manifold bolts. Fabricate a small bracket between these bolts to guide the throttle cable cleanly. Route the cable from the pedal down to the front lever.

The result is a significantly shorter cable run, less slack, crisper throttle response and no cable movement over bumps. Five minutes of work with a hand drill or the option to purchase a ready-made bracket.

Fuel Pressure Monitoring

Do not connect boost pressure to the fuel pressure regulator. Static three bar is correct and sufficient for all power levels on these engines. A boost-referenced regulator adds complexity with no meaningful benefit and introduces another potential failure point.

What is worth doing is fitting a fuel pressure gauge or logging fuel pressure electronically during initial setup and testing. Specifically during wide open throttle pulls at full boost verify that fuel pressure remains stable at three bar throughout. If pressure drops under load the fuel system cannot supply sufficient volume – pump capacity, filter restriction or line sizing needs attention.

Rock solid three bar throughout a full boost pull confirms the fuel system is correctly sized for the power level being run.

Summary

• OM606 injection pump throttle lever: stock rear lever causes cable slack and imprecise response
• Front lever on opposite end of pump shaft provides shorter cable run and crisp throttle feel
• Set lever position at full throttle horizontally, use intake manifold bolts for cable bracket
• Fuel system: electric pump, pre and post filters, injection pump, return regulator at three bar
• Static three bar fuel pressure – no boost reference needed
• Log fuel pressure during testing to verify system can supply adequate volume at full boost
• Injection pump elements are precision components – buy from builders who genuinely know these pumps

DIESEL for life. Love you all. See you another day – not from the car!