What fuel system does the diesel engines model have?
CREATE TABLE "engines" (
  "model" text,
  "engine" text,
  "displacement" text,
  "valvetrain" text,
  "fuel_system" text,
  "max_power_at_rpm" text,
  "max_torque_at_rpm" text,
  "years" text
);
SELECT "fuel_system" FROM "engines" WHERE "model"='diesel engines';