Fuel pump problem

Recently had to replace a heater core in my 1989 Mustang LX 5.0 HB.I removed the dash and HVAC etc following a mechanics manual.I got everything back together fine but now i have no response from the electric fuel pump.When the key is turned a sound should emit as the fuel pump "charges" for a few seconds.Ive tested the fuseable link and have 12 volts,i checked the fuel relay under the drivers seat and got random Voltage # readings from the black/pink wire.The enertia switch wasnt tripped that i know of and i tested that it "seems" ok.Following some advice i ground the EEC TEST port for the fuel system and attempted to fool the computer into running the pump, doing this only caused a clicking sound at the relay under the seat.The car ran fine prior to the dash and instrument cluster removal.I dbl checked for any plugs hanging loose i may of missed-nothing thats visible all "looks" ok.Im at a loss and only a back yard mechanic.Anything i could further check?The fuel pump should be fine unless somehow it blew while the heater core repair was done but the car never ran during that time.If anyone can offer help please describe any process like you would to a 3 year old!!!-- as thorough as possible please ..thanks!

Thanks for that info, im heading back to the shop ina bit and i will certainly check that, it is worth a try.

Fixed

Thanks guys for the input much appreciated, i found the problem was with the relay under the drivers seat, the orange/light blue wire was badly corroded inside the plug fitting ( like green and gooey corroded) it had actually broken off but hung inside the fitting a bit.I cleaned it up and rewired it and it works now.Id of been paying the shop big bucks+ tow truck or banging my head for days without the help so thanks again.