injecting shad body leaving body hoolow

this is my first time make my own lures. Ive never had any dealings with injection molds. I made a shad body injection mold at work other night and when I inject it the tails fill out nicely but almost all the bodies are hollow. Sometimes the tail will fill then nothing in the body and the sprue will be completely filled out. like I said ive never done anything like this before and have actually never seen a injection mold before. m sprue is 1/4 diameter. My Im thinking it could be vent problem only vent I have is in the tail. I burp the injector before I shoot so I don't think that's the problem. thanks for any help

When you made your mold you didn’t make enough venting so the air can escape if I get time I will post a picture of a mold with cross venting .

Is the fill port big enough to hold excess to allow for shrinkage and pointed up?

The fill port is about .300 deep and the injector fits really good. I think maybe most of my problem is that I had some powder coat powder left over from when I use to powder coat. I used some of it to add color to the plastic. I’m thinking that when it was heated up that much it must produce a gas and that’s what is causing some of my problem. So I think I definitely need more vents. I injected a few tonight with new plastic without the powder and it did a whole lot better. That being said I think I will still add more vents to my mold. Learning curve making my own!!!