GM-GMC: starting problem and smoking master cylinder, gmc 1500, master cylinder

Question
my 89 gmc 1500 reg cab long box truck has all of a sudden had problems starting it turns over very slow like the battery is almost dead but its not dead. so i poped the hood and had my wife turn it over and as she tried to start the truck i noticed some smoke coming from the master cylinder. i hopped in the truck and turned the key it did same thing so i applied the breaks and it fired right up. it used to do this occasionally but now it s every time plus sometimes applying the breaks does not help. please help me thanks for your time

Answer
That is one of the strangest cases I have heard in a while.  The smoke, to me, indicates that the master cylinder is conducting current from some where.  Check your main battery grounds, ensure that there is no corrosion where they attach to the frame or block. If that ground is bad, the ground may be finding its path through the master cylinder.  Also check to ensure the starter is grounding properly to the block.  If you are electrically inclined this can also be done by doing voltage drop checks from the battery to the block and from the starter motor housing to the battery.
Hope this helps