Like it was said, I can't really take for the other ENFP's…
But I'm a great feeler (if this makes sense, hahah). When I'm going through a healthy phase, I can quickly tune in to other's feelings and needs. When I'm into someone, I try to get to know this person better, try to get closer. I talk to that person about absolutely everything and I like to make people feel comfortable around me. I like to make them laugh (usually with self-deprecating jokes hahah) and make them feel great about themselves. I like to talk and sometimes insert a small flirtatious comment and see how they react. I like to draw in every detail about the person. I like to watch people, how they move, their unique habits. I like to discover what makes them passionate. I like to know how their souls flare up to a song, a sunset or to a poem. And I'm usually pretty timid and humble to them.
But that's when I reeeaaaally am into someone. People tell me I'm quite magnetic, but I rarely am interested in anyone. So I just shoot for small talk and casual stuff.
Mostly, it's because getting people to grow attached to me makes my ego jump around. Unhealthy ENFP's tend to be a little manipulative to get attention sometimes, to get you coming for them.
If I really am into someone, I tend to answer messages really fast. I hate to keep people I like waiting. There's this feel to make them feel loved right away. Otherwise, I just answer people whenever I feel like.
But you can confront him and make it clear for him. If he's like me, he'll try to hide it and fail. Because we want to look cool and distant, when we trully are goofballs who love attention. And getting the attention from who we really like feels like an excited Golden Retriever puppy getting belly rubs. If he really is into you, he'll be excited, but will be too shy to actually show it. If you squeeze it from him, maybe he'll show you this embarassed side and confess. That's if he thinks and acts like me, though.
I hope I was able to help and i'll be cheering out for you!