There are remedial additives which un-gel diesel that has blocked the fuel lines. AMSOIL Diesel Recovery Emergency Fuel Treatment is one of the most recommended fuel treatments that dissolve the wax crystals that form when diesel fuel has exceeded its cloud point.
Gelling happens when fuel reaches a low temperature whereby wax crystals have formed that restrict any movement in the oil. For #2 diesel, the temperature is usually around 17.5 °F (−8.1 °C).
TIP: It’s better to prevent than to cure. Add a product like Power Service, an advanced diesel fuel additive that will prevent gelling. Use Diesel 911 to solve your diesel fuel emergencies during the cold winter months.
Along with the anti-gel additives, drivers drape some blankets or tarps over and down the sides of the car and stick a heater to blow heat down there, the blankets not only contain the heat, but they also keep the wind out.
In FleetNews, a diesel biofuel content is the suspected cause of unexpected winter breakdowns. Find more details here.