Which statement is true regarding a closed type fuel injection nozzle?

The statement that most closed nozzles open by differential area of the needle valve is based on the fundamental design and operation of closed type fuel injection nozzles. In a closed nozzle system, the opening mechanism relies on differences in pressure exerted on different areas of the needle valve. When fuel pressure builds up to a certain level, the pressure acting on the larger area of the needle valve overcomes the spring force holding it closed, allowing the nozzle to open and inject fuel into the combustion chamber. This differential pressure mechanism is essential for precise fuel injection timing and delivery, making it critical in the operation of diesel engines and similar systems.

The other choices present various attributes of fuel injection nozzles that do not accurately align with the characteristics of closed type nozzles. For instance, while hole-type nozzles can exhibit self-cleaning properties at times due to fuel flow, this is not a definitive feature applicable universally across all designs. Additionally, saying that multi-hole types are exclusively for precombustion chambers is misleading, since they can also be used in direct injection systems for improved atomization. Lastly, while pintle types may face issues with carbon deposits, this condition is influenced by various engine operating conditions and is not unique or predominant to