Fuel

It should have a pretty obviously fouled spark plug.

Any applicable trouble codes? Do an ohms test on injectors, 13.3--15.7 ohms@ around 70 degrees. Does the vehicle start and run?

An Ohm test isn't going to tell you if the injector is stuck open.

If the ohms test reads all zeros, I think the injector is faulty. Yes it could be mechanical. If the cylinder is filled up with gas, it won't even crank. I agree, if the spark plug is dripping gas, check that cylinder. I asked if the vehicle would run, he could do a cylinder balance test. I didn't see your post before hand, but, whatever. Have a good day.