8000 coleman generator run but no power output

You need to consult a local electrician, if you do this wrong you can cause allot of damage. We can only guess as to the correct way to do this without being there and looking at the wiring setup.

http://www.advanced-power-technologies.com/coleman-power-station-generator.php

It can be many things can you be more specific please, no voltage on either leg of the 240V, zero voltage or a small amount

If the engine is running with the alternator not outputting then you must check with the LOAD TRIP switch.
if not remove the load and check if there is output. If not there is fault in tha alternator which might need some consensus.

My owners manual says to take it to a service center to get the generator "excited" if it has no brushes. Hope this helps

The lack of DC output COULD possibly prevent the stopping. There are likely fuse(s) between the low voltage winding and a rectifier to generate the DC. SOMETIMES these are even inside the generator cover.

After working on several of this style coleman generator,i have found that the lead wires in the windings that are soldered to where your brushes would contact tend to break.I don't know if it's a poor design or just a fluke,i would check to see if your getting continuity on the rotor and go from there.They seem to either "burn off" or just break.

The generator needs to be 'flashed' to bring back the excitation for output. Is this something you can do? Let me know and I can help you...

If you need further help, I’m available over the phone at https://www.6ya.com/expert/craig_3fa289bf857b1a3c

Visit this site http://www.perr.com/phpBB3/ and they can tell you how to flash your generator. Might I suggest you run the generator often and put it under load even if you're not depending on its power output at the time like you would in a power outage. Like use it to power a shopvac or similar device.

Try replacing the capacitor. You can buy it from http://www.jackssmallengines.com/do_it_home.html. When you pull off the power end of the generator look at the diodes also. If they look toasted replace them as well