Is the injector pre or post butterfly valve? Assuming that it's similar to an automotive throttle body fuel injection system, that puts the injector before the butterfly valve. In that case, it could be the butterfly valve. But if it's similar to mine, it's a mechanical butterfly valve, and should be opening and closing via a cable. You can check that.
You mentioned that the coil is getting power. Have you confirmed that the spark plug is actually firing? Maybe it's a overhead valve out of adjustment?
Just spitballing here, trying to help.