Once u find the cyl/injector that’s suspect, u can move it to another cyl or hook it up OUTSIDE the engine..to watch the spray pattern..
BE VERY CAREFUL WHEN YOU DO THIS.!!! The SPRAY FROM THE TIP CAN AND WILL PENETRATE YOUR SKIN AND GIVE U BLOOD POISONING.!!!
No need to worry about it just loosening the lines..
UNLESS your working on a tier 4-5 engine..