Water or foreign substance is mixed.

Solvent or chemical substance is mixed.

Gasoline or kerosene is mixed.

Corrosion, wear, blocking, sticking (in the fuel system)

Carbon deposit in the injector nozzle and a combustion chamber by incomplete combustion.

Excessive black smoke by incomplete combustion.

Catalytic system is damaged by incomplete combustion, especially CPF could be damaged.

Solidification of paraffin wax added in the diesel for viscosity and lubrication. (Hard starting in the winter)

IG KEY "OFF", ENGINE "OFF"

Prepare a clean beaker. (For receiving diesel fuel).

Remove the fuel filter assembly.

Remove the water separator sensor from the fuel filter.

Inspect the diesel fuel (Foreign or metallic substances, water etc...from receiving diesel fuel in the beaker).

☞ Metallic substances could be found by magnetic.

Inspect the diesel fuel color (Too transparent or too red color is not good) in the beaker.

☞ Diesel fuel color would be different by oil companies.