I noticed constant air bubbles in the Diesel Fuel line to the Injector Pump. Is this normal? Or does it indicate that air is getting into the fuel line? Noticed at high speeds uphill, the RPM's drop off.

 

Check your injector pump. It is probably disfunctional. Check any tubes that have to do with your fuel system. Check for holes. I've never had this problem before. Ask around. I'm sure u can figure it out.

 

cracked or leaking pipes around the filter. take it off, bi-pass the filter, see if the bubbles disappear.

if not, check fuel sender unit. should have part number 1J0919183H. if it ends in C or D, then they are prone to go wrong, blocking the small hole. there is also talk of biodiesel blocking the sender due to swelling og o-ring, and cold weather not helping. check the number, either drill it out or get the new part. check tdiforum, they have all the details.