no fuel pulse on start up??

Hi all new to forum.

I have a 89 S10 4.3 tbi 4x4 truck
I got the fuel pump for 2 sec when I turn key to on
but when motor is cold I need to pump the gas to get the injectors to pump fuel?
but when its warm it fires right off?
It all started when I changed my heater core and themostat.
I loosend my dash and pulled it out a bit on the passenger side.
I have replaced:
fuel pump relay
ignition module

Is there a ground strap I may have off in the dash area? Is there a ground strap for the ecm?

i have a 91 s-10 my fuel pump is going out so i do this. first turn on your key to listen for fuel pump don't try to start it tho do this turn on and off about three times then on the forth time go ahead and try turning it over and it should start...good luck... since you put new fuel pump on can you really hear it go zip until it gets to the engine? i use to have to put wire dry on all plug wires they looked good and when i checked wires at night there was no cross fire so they were broke down inside. and in summer time it would start right up but when it seen snow i had to crank and pump the hell out of it then i figured out the fuel pump i do what i told you to try. have you cleaned throttle body out?

I would use a pressure gage and check system fuel pressure either the pressure regulator or pump could be going bad.