How A Diesel Fuel Injector Works
 

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No.1 - Leak off Port, a hole to release pressure from the injector if/ when it needs changing.
No.2 – Leak off cap, a cap which screws on to the top of the keep the spring compressed.
No.3 – Injector Spring, a helical coil compression spring, which is in-between the ‘spring cap adjustment nut’ (No.18) and the ‘Spindle’ (No.16). It is held in place by both upper and lower spring plates. The spring’s job is to keep the ‘Needle Valve’ (No.13) closed until the appropriate fuel pressure is reached, also to close the ‘Needle Valve’ (No.13) when the fuel pressure drops.
No.4 – Lower Spring Plate, retains the injector spring
No.5 – Clamping Flange, the injector is supported by this flange
No.6 – Nozzle Holder, this is a forged-steel flanged housing which supports various parts; it is bolted to the engines cylinder head. It has a threaded inlet port to support an inlet adaptor; a supply hole is drilled to intersect the pressure face junction between the ‘Nozzle Holder’ (No.6) and the ‘Nozzle Body’ (No.9). The upper end has a large threaded countersunk hole made to support the spring cap adjustment nut.
No.7 – Fuel Gallery, the storage chamber to hold the fuel which has been pumped to the injector before injection
No.8 – Tapered Needle Shoulder, the tapered needle shoulder is actually tapered so that the fuel can smoothly and quickly pass by when being injected.
No.9 – Nozzle Body, this supports the ‘Needle Valve’ (No.13), it is cylindrical in shape and has a centrally bored steel body. The bottom of the centrally blind hole is conically ground to form the ‘Nozzle Valve Seat’ (No.12).
No.10 – Spray holes, these are the holes in the end of the nozzle. These are drilled at various angles to suit the combustion chamber on a multi-hole type nozzle.
No.11 – Nozzle Tip, The extreme end of the nozzle body containing spray holes.
No.12 – Needle and Nozzle seat, this determines how much fuel flows to the combustion chamber.
No.13 – Needle Valve, this has two sections of different diameters. The bigger of the two diameters forms a lapped fit with the ‘Nozzle Body’ (No.9). The smaller diameter has a large clearance between it and the ‘Nozzle Body’ (No.9), its 60 inclusive angle conical ground end forms the ‘Needle valve seat’ (No.12).
No.14 – Feed hole, where the fuel is fed from.
No.15 – Supply Hole, the hole that is responsible for taking the fuel from the inlet port to one of three feed holes.
No.16 – Spindle, the ‘spindle’ relays the spring thrust to the needle valve from the spring, it is placed in-between the ‘spring-cap adjustment nut’ (No.18) and the countersunk threaded hole in the ‘Nozzle holder’ (No.6), it forces the ‘Needle Valve‘ (No.13) onto the nozzle body seat.
No.17 – Inlet Port, the port in which the fuel is fed into one of the three feed holes.
No.18 – Spring Cap Adjustment Nut, to adjust the amount of pressure in which the injector injects fuel into the combustion chamber or the swirl chamber.

thanks i need all the help i can get

I'm a Dummy, is this for the mechanical injectors or the electronic ones, or do they all work the same way.

They pretty much work the came way other than common rail a electrical inpulse is sent to the injector making it pop in stead of the "old school" injector only pops when the injector pump pushes the fuel to it. Common rail has about 20,000psi at the injector at all time which is the need for the inpulse (hz). Mechanical only pops when the pressure from the pump is pushed to it (one at a time) and 5.9l cummins 24v is suppost to pop at about 4500)psi. So the common rail is more effective in the spray, more pressure better atomiziation. Fords injectors are a whole different story and duramax uses a common rail pump as the newer cummins does.

one works on fluid pressure to pop it off the other is electric impulse

I love the Bosch Piezo injectors of the Common rail - Thats real high tech.

And a simpler, more efficient and easier to troubleshoot way of doing it than earlier pop-pressure systems. If the ECM fires the injector and the CP3 makes pressure, it runs.