84' S-10 with a 89' 4.3 motor swap

I have an 84' S-10 witch was a 2.8 but recently turned into a 4.3 fule injected. to do this we had to swap everything from the wiring harnness to the whole dash. my question is the dash now somtimes will cut out but when hit hard by my hand will come back on. its a digital dash and everything wired up right and tight... whats going on with it?

Sounds like a loose/corroded connection.

check and clean all connections. if you have to hit it something is loose.