I don't know of this body horror movie i used to own?

the movie was probably made in the 1980's it's about aliens that crashed into earth in the woods in the 60's? a group of teenager's went to investage it was a spaceship. the pit then opens. I can't remember the rest but i do remember their were 4 teens. Two guy's and two girl's. they have the aliens in them. i also remember in the last part that some guy get's runned over by a train but he did not completely die he get's reborn and his body rebuilds to new it reminded me of hellraiser 1. The cover the movie box has some creature that looks like crang from the ninja turtles cartoon if i remember? this movie is not a cartoon. It's like one of those live movies like jason goes to hell or dawn of the dead.