I was having a similar problem. I wouldn't get a full lasting erection or none at all. I discovered that the needle I was using is too long so I experimented with different sizes. A standard long needle goes too deep. It has to go into erection cavity. If it goes to deep or not deep enough then Trim...

I tried the pump and couldn't get a solid erection. I discovered that the big problem is that even when I'm not erect I'm too fat for the tub so there is not enough room for my penis to expand and draw blood. I'm told I can get a wider tube.