Volkswagen Repair: starting problem, jetta tdi, air bubbles

Question
I have a 98 jetta, tdi, I use 100% biodiesel for over a year now only in the warmer months. (I live in Pa. and use it from april till Oct) I never had any problems till the other day I went out and it just wouldn't start. I have a new battery, it has plenty of cranking power, I changed the fuel filter and it still won't start. Any suggestions would be greatly appreciated. Thank you

Answer
Hi there Liz;
The only thing I can think of to suggest at this point is to just barely crack open the fuel lines at the injectors just to make sure there aren't any air bubbles in the system.  If there was any air that got in when the filter was changed, it will take a long time to get them out.  This is the quickest diagnostic tool to see that.  If you have a good flow of fuel at the injectors, then about the only other thing I can think of off hand is the pump.  If the pump now has air in it it will take a lot of cranking to get it out, and the opening of the injector feeds will help tell you this too.  Unfortunately, many times when a fuel filter is changed on the TDI engines the fuel filter is put on dry, and that causes the problems you are describing now.  The way we do it at the shop is to get the old filter off, hold it upright, and then hold it over the new one, and open the little white water drain at the bottom for just a second to get the water out, then open it over the new filter, and let the old one fill the new one.  This causes fewer problems when changing filters.  Hope this helps you get back on the road, Liz.