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Old 10-09-2013, 05:23 PM
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funola funola is offline
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Join Date: May 2005
Location: NYC
Posts: 8,243
Originally Posted by kerry View Post
Wouldn't the lift pump do the same thing but it's not delivering fuel to the secondary filter at all.
If there is a pinhole leak in the fuel line (I am talking about a very small rust pinhole in the fuel line that barely weeps when engine is off), the lift pump will still draw fuel plus air, just like the primer pump will. Depending on the severity of the amount of air getting in (dependent on the size of the pinhole), the engine may be hard to start or not start at all, or run ok or very rough or stall out.

The best tool for quickly diagnosing if there is air in fuel is a clear section of fuel line at the cigar hose. It should be solid stream of fuel there. If air is getting in, it will end of there and be easily seen.
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked
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