I own a 6.7 so they have a solenoid on it. Anyways I was wondering how a 3rd gen knows when to fire the injectors. Also what year was common rail introduced for cummins engine?

Cummins went to the Common Rail in USA / Dodge in 03

Prefect video of it...

http://www.youtube.com/watch?v=aGwV9ueHcz4

1989-1993 1st Gen (VE Rotary injection pump)1994-1998 2nd Gen (P7100 Inline injection pump)1998.5-2002 2nd Gen (VP44 Rotary electronic injection pump)2003-Current 3rd and 4th Gen (Common rail injection)

Pre-CR the injectors were fired by fuel pressure. The pump would pressurize the fuel in firing order (why pre-CR pumps are timed, and a CR isn't). The fuel would reach "x" pressure (300 bar comes to mind, or ~4500 psi) the fuel pressure would overcome the spring pressure and the injector would open. The fuel pump would send a specific amount of fuel to each injector and as soon as the pressure dropped below "x" the injector would close. This is also why the injector lines on pre-CR trucks are equal length, and why they are different on a CR.

Dang... I should of posted this...

As for the fuel pressure is sent down to the nozzle lift the pintle against the spring once the VP44 moves on to the next the pressure fades and closed against the spring. This all happens very rapidly.

So does a 5.9 2006 have solenoid valves on top?

2003 to current date have solenoid on top or Common Rail Injectors...

12-valve injector (2nd Gen P-7100 pumped)

24-valve injector (2nd Gen VP44 pumped)

24-valve Common Rail injector (3rd Gen CP3 pumped)

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Thanks everyone!

Do the fuel lines connect directly to the p7100 injectors without cross over tubes?

Do the fuel lines connect directly to the p7100 injectors without cross over tubes?

All 12V engine have the injection lines directly to the injector. The return rail is also external of the engine too.