Common rail engine won't start

What is the engine in? This is an automotive repair forum, so most of us in here don't deal with generator or boat engines.

If this is computer controlled and you keep getting a trouble code for engine speed input. You should test to see if your getting a signal at the engine computer connector for that circuit. You'll probably need the wiring diagram and you'll need to determine what kind of sensor design is being used. Most car and truck engines use either hall effect, VR, or optical sensors for speed and positioning.

You would want to put an oscilloscope on the signal wire of the sensors to see if they are indeed generating a signal during cranking. Don't know about this engine particularly, but quite a few diesels with electronic controls will not inject fuel unless cranking at least 250 RPM.

I do not have access to tech data for what you have so I couldn't be too specific. I would hold off on blaming the controller just yet, you could be throwing money away if you don't make sure you have the right diagnosis. The engine manufacturer will have troubleshooting guides and wiring diagrams for this, although I doubt you will get them for free. You would want to see what is working and what isn't. For instance, if this is a 5v reference sensor you need to ensure you have the 5v reference at the sensor. If not you need to find out if the ecm is generating it. You say it happens with just the key on, so that likely rules out an issue with a tone wheel . You could easily have a failed seal on a connector somewhere in the wiring that has allowed dirt or moisture in and is causing this, or a bad wire somewhere. Thats where having the right data from the manufacturer comes into play. Bosch made the injectors and ecm, but they made it for the engine company. You need the engine company to give you the wiring info and such. Once you have that you can make systematic checks to be confident that you are spending your money on the right part that will definitely fix this issue for you.

Start with the scope test, but you'll want the wiring diagram to know where to hook the scope into anyhow.

I'm definitely not a diesel engine tech, but I don't understand why that engine speed code would be showing up if you have a problem with fuel pressure. Is that solenoid that you unplugged duty cycled to control the amount of fuel going to the high pressure pump?