Erection and ejaculation are two separate neurological reflexes. We all know we get boners without cumming. If the plumbing is messed up, or if the sympathetic nervous system is messed up, y'ain't gonna get hard. BUT that doesn't necessarily mean you aren't going to be able to ejaculate. Hell, very early in my game I was a premature ejaculator. Fear, anxiety, desperation, on one occasion resulted in Mr Softee spraying my girlfriend's pussy with rapid fire jets of hot, sticky ejaculate. All I was doing was positioning my dick above the clam, hoping desperately to be able to get hard for the penetration part. I was soft as rain, and guiding with my fingers, no pumping or anything. I just went off spontaneously. Great girl!