Ichanged a engine in a 99 blazer,same engine 4.3 .you turn the key to start and it does nothing,check all wires and they are all hooked up.cant figure it out any help would be so great

 

There could be a number of problems that pop up after a motor swap and it can be difficult to pinpoint without being there. The more information that you can give the better.

Do your dash lights and headlights ect come on when you turn the key?
If they do, do they dim when you try to crank the engine over?
Any noises at all from the truck when you turn the key or when you try to crank it? For example you should hear the fuel pump kick in as well as a few servo type motors such as the IAC kicking in.

 

When I swapped my engine my friend hooked up the starter wrong and then broke the small signal wire. If nothing is happening and all the lights are coming on, start there.