Mercedes-Benz W140 OM606: air in the fuel lines
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W140 OM606 misfires at idle and there are air bubbles in the fuel line, where does the air come from?
A typical place for an air leak is the O-rings of the transparent tubes in the fuel lines. When the rings were replaced, the air bubbles and the idle misfiring stopped. There must be no air at all in the lines.
Why does a small air leak affect the running of the OM606 engine?
There is no electric transfer pump. The only transfer pump is on the side of the feed pump, and it draws fuel from the tank by vacuum. That is why even a small air leak disturbs the running.
Where are the leaks near the injectors checked on the W140 OM606?
Remove the plastic cover from on top of the valve cover and check the injector leak-off hoses. If there is fuel in the hoses or around the injectors, replace the hoses with new ones.
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