The injectors are constant live, and pulsed by the ECU, I doubt you can check via a multimeter, as it will be to fast for most of them to capture, ideally you would use NOID lights.

Check the injector grounds to see if one has shorted.

What Tony means is check the power at the connector, using the battery for the ground connection, i.e. so only your positive probe should on the injector LIVE wire at the connector.

Martin