The illustrated device is operated directly...

🔍 Key Concepts

• Identify the type of device shown (note the spring-loaded needle and nozzle at the tip). • Consider what force must overcome the large compression spring in order to lift the internal valve/needle off its seat. • Think about how fuel is normally metered and timed into a diesel cylinder: is it by mechanical linkage at the injector, by fluid pressure, or by combustion pressure after ignition?

💭 Think About

• Look closely at where the side connection leads and what part it acts on inside the device. What medium would come through that connection during engine operation? • Ask yourself: which of the choices would act directly on the needle inside this device, and which would act somewhere else in the valve train or combustion space? • For each choice, picture the path of force from the source (rocker arm, cam, fuel, combustion gases) to the needle. Which one has the most direct, straight-line action as drawn?

✅ Before You Answer

• Verify which option supplies a pressure or force directly into the body of the device through the angled fitting. • Confirm that no external linkage (like a rocker arm, push rod, or cam follower) is drawn in the illustration. • Check that the device operates before combustion occurs, so it cannot rely on combustion pressure to open it.

The illustrated device is operated directly by __________. Illustration MO-0041

a rocker arm and push rod

fuel oil pressure

cam action

excessively high combustion pressure

🔍 Key Concepts

💭 Think About

✅ Before You Answer