Haed Starting And Rough Idle

I HAVE A 1995 GMC SONOMA 2.2L AND I AM HAVING TROUBLE STARTING IT WHEN COLD WANTS TO START BUT JUST WONT I PUT A NEW FUEL PUMP AND SENDING UNIT IN AND STILL DOESNT WANT TO START ALSO COOLANT COMES OUT OF THE OVER FLO TANK SYSTEM STAYS PREASURIZED WHEN COLD CAN ANYONE HELP:confused:

Remove the radiator cap and watch for bubbles in the radiator when an assistant tries to start the engine. If you see bubbles, or the coolant comes whooshing out when trying to start it, you have a blown head gasket.