Have not experienced this personally, but if you are showing air in the lines then my first thought is the fuel lines and their O-rings leaking.

There are several threads here that address similiar issues.

How many miles are on yours?

Have you had the glowplugs replaced? (I know sounds odd but if it turns out to be fuel lines are leaking, if you change those you will certainly want to address the glowplugs as that is the other "issue" with the 606 and stuck glowplugs)

Let me check some old links I have saved and report back.

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raMBow

1999 E300DT Obsydian Black Metallic, Heated Full Leather Parchment options, E2, K2, 136,000+, best 36.5 mpg - GP's 12-04 & 11-12 Zero Stuck
2010 Honda Odyssey - The BrideMobile - best 26.5
(2) 2005 Honday Accord- (1 -Corporate 1 - Personal) - 110,000 4-cyl 30mpg
2000 VW Golf GLS TDI, Upsolute Chip (sold to Brother, now 300+k on it) 48.5 mpg like clock work
1987 Honda CRX HF - Sold 87,000 always over 50 mpg Max 67 mpg