John 6:46: No one has seen the Father except the one who is from God; only he has seen the Father.
According to John 1:18, "No man has seen God at any time, the only begotten God/NASB, who is in the bosom of the Father, He has explained Him."
The "fulness" of God as stated in vs16 could not be known through any ordinary man. It must come through the One who possesses the nature of God. The word "God" is stated first and is without the definite article. This indicates first, that the emphasis is on the word "God" and second, the nature of God is the object of our attention.
John 4:24 is teaching that God is a spiritual being. At John 14:8 Philip said to Him/Jesus, "Lord show us the Father, and it is enough for us." Verse 9, "Jesus said to him, "Have I been so long with you, and you have not come to know Me, Philip? He who has seen Me has seen the Father; how do you say, Show us the Father?"
This is "NOT" teaching that Jesus Christ is God the Father. It's teaching that the Father has no separate manifestation from the Son. The Son is the "ONLY" manifestation and revelation of the Father.
What is know of the Father is revealed through the Son. To see the Son is to see the essence of the Father. (John 1:18; John 10:30, John 12:45; Colossians 1:15, Hebrews 1:3.)