Here are some of the simple things that are most common. Some have been covered.
Your
engine was running before you changed the fuel filters, right? Rough but running, right?
Your stop cable or selenoid might be in the wrong position to start your engine.
When you crank your engine to bleed the injectors you may run down your
battery and the engine will not spin fast enough to get enough
compression quickly to fire. You need to start with a fully charged
battery.
You may still have air in your fuel lines. The least little bit of air will prevent the injectors from delivering the proper spray pattern into the cylinder to get it to fire.
You can bleed your fuel lines to the injection
pump by the primer hand
pump but from that point from injection pump to injector you must push the starter button and open the nut on top the injector simultaneously until there are no bubbles in your fuel supply at the injector. Then you must tighten that nut before you stop the engine from spinning. Doing one injector at a time will keep you from running your starter
motor too much. This is very hard to do by yourself unless your starter button is in the engine room. You need a partner who will push the starter button while you are opening and closing the nut on the injector.
Make certain your
cooling water supply is closed so you don't flood your engine with
water. Once your engine is running then open that supply quickly to prevent damage to your
water pump cooling vanes.
Do you have an
electric fuel pump in the fuel line before your filters? Is it pushing fuel through your system to the injection pump?
If you suspect your fuel supply or your filter connections then disconnect your fuel supply line to the
injector pump and attach a very clean separate supply (fuel can or
outboard motor tank with
diesel in it). Mount it higher than your engine to supply gravity feed.
I would do all of these things before starting to take
parts off your engine. Yes, your injectors might need testing but that might not be why you can't get it running.
Good luck. I hope others reply and set me straight if I've given the wrong
advice.