🔍 Key Concepts

• Effective stroke vs total stroke in a port-and-helix fuel injection pump • How the helix and control rack change when fuel starts and stops flowing • Which parts change quantity of fuel delivered on each stroke, and which are fixed by design

💭 Think About

• Think about what actually changes from minimum to maximum fuel delivery in this type of pump—what is the operator or governor really moving? • Which option controls the start and end of fuel delivery during the plunger’s upstroke, rather than just the size or speed of the pump? • If the pump plunger always travels the same mechanical distance, what could still change to alter the effective pumping portion of that stroke?

✅ Before You Answer

• Identify which option directly alters the timing of port closure and opening during the plunger stroke • Separate items that are fixed by design (do not move during operation) from those that are adjustable during operation • Verify which component is used by the governor/throttle to regulate fuel quantity in a port-and-helix system