Novice Chest/Biceps Question

Hey guys for the past few months i've been trying Chest/Shoulder/Biceps routine and i've found that i personally like it much more than the chest/triceps one.
Im having a question though and although i searched quite a lot i couldnt find the answer to it.
I start that specific day with chest work,then with some shoulder isolation and then with biceps.For the past 2-5 workouts after im done with my biceps i did some extra chest exercises and found out that when my arm is pumped i feel my chest a lot more during presses and flyes.

Could anyone explain to me whats going on i literally cant find any answer and im not that knowledgeable as well

Possibly your biceps are fatigued so the weight is hitting the chest directly. Obviously we use our arms slightly when doing chest exercises but if they are completely fatigued your chest has no choice but to move the weight therefore your feeling it more. Think I understand the question hope that helps a bit

Thanks for the help.
I was also wondering if chest activation is essentially the same either when i do chest free and when i do it after biceps?Dont know if activation equals feeling the muscle.
Also if the latter is the case would you recommend doing chest moves entirely after biceps or should i do isolations when fresh and compounds after hitting biceps since it would help target the chest more efficiently.
Quite ironically chest is my weakest point and its the one bodypart that i get the less pump to when training.
Sorry for the lengthy reply but i would really like some help for chest training as i've literally tried anything.

Btw current routine is
4 sets incline db bench
3 sets decline db bench
2-3 sets flat db fly

If chest is a weak body part I would always do it first when you have more energy. I think your problem is the mind to muscle connection your lacking. I would decrease the weights and concentrate on form until you get the feeling of your chest being worked. Far too many times people lift with their ego and don't concentrate on what muscle they are actually trying to train.
Drop the weight, get the right feel then you can add weight. Hope this helps bud good luck

^^^^^^^^yes to that kai green talking about the stretch and contraction in one of his videos on YouTube he curls 20lbs

went to the gym just an hour ago
Started with shoulders,then did biceps and then i started my chest with db flyes.Then went on to a machine chest press (the one that as u come up u go in a bit) and then finished with incline db bench.Felt so damn good both during and after the workout im literally typing this on my keyboard and when i try to move my arms a bit like in a fly motion i can feel the chest worked.

Good to hear buddy