Cars using biofuel typically have problems with injection pump failures; symptoms can include a "no start" condition or external pump leaks.
Car Problem Reports
Volkswagen Jetta TDI Vehicles Using Biofuels May Have Injection Pump Failures
Volkswagen Jetta TDI Problem
Engine Affected: 1.9L 4 Cylinder Diesel Turbo
varies miles...have resealed many leaking pumps. typically with biofuel and diesel use this will occur sooner than vehicles running just one or the other.
Visitor, 2000 Volkswagen Jetta TDI, 1.9L 4 Cylinder Diesel Turbo, 135,000 mi
Fuel found after vehicle parked. Poor MPG. Inspected IP could see leak. Decided to install rebuilt injection pump and timing belt/water pump instead of just replace IP seals. Get rebuilds done at DFIS in Portland, OR.