any info on c class drawing air ? some thing to do with fuel delivery system in tank

More likely is a problem with the o-ring seals at the fuel lines feeding the fuel filter and Injection Pump.

If its a problem at the fuel tank, it could be failing the "large" vapor self test.

This is a CDI engine? Which one?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

car runs ok when you put two pipes in tank by passing sender units seams to be vacume system set up by pressure from hi pressure pump whitch equalizes fuel taken from both sides of tank cdi engine 2004 1800cc