🔍 Key Concepts

• Trace where passage connected to piece #38 leads inside the injector body and whether it returns fuel or blocks it. • Think about the difference between a filter element, an adjusting screw, and a spring-loaded relief or regulating valve in a fuel system. • Consider how excess high-pressure fuel is safely handled in a diesel injector system so that nozzle and pump parts are protected.

💭 Think About

• Look at the small spring and valve parts (#39 and #40) that work together with #38. What kind of component typically uses a spring pressing on a small valve in a fuel system? • If #38 were a filter, where in the flow path would you expect it to be located relative to the fuel inlet? Does the drawing support that? • Ask yourself whether the device associated with #38 seems to control pressure at a constant value, or mainly to open when pressure gets too high and send fuel somewhere else.

✅ Before You Answer

• Verify whether #38 has any visible filtering media or screen shown in the drawing. • Check if the passage from #38 leads back toward the low-pressure/suction side or simply sits in the high-pressure line. • Confirm whether #39 (the spring) appears to be adjustable from outside, or just fixed to let a valve open at a set pressure.