CREATE TABLE table_63835 ("Model" TEXT, "Engine" TEXT, "Displacement" TEXT, "Valvetrain" TEXT, "Fuel system" TEXT, "Max. power at rpm" TEXT, "Max. torque at rpm" TEXT, "Years" TEXT)

What fuel system does the diesel engines model have?
SELECT "Fuel system" FROM table_63835 WHERE "Model" = 'diesel engines'
SELECT "Fuel system" FROM "table_63835" WHERE "Model" = 'diesel engines'