Wow!
System should be evacuated first. This removes moisture which will 1) cause corrosion in the system and 2) greatly reduce system efficiency.
Make damned certain you're hooking your death kit up to the LOW side port, not the high side port. Only a well-trained person with the correct equipment should do high-side port service filling.
The system should be charged with the can upright, not turned upside down. If you don't know why, you have no business screwing with an AC system.
System capacity is listed either on an underhood label or in the service manual. Do not exceed this amount. If you overcharge the system, it will work just as badly as if it is undercharged, if at all.
Get a manifold guage set so you can monitor both sides of the system. Then, you'll know what's actually going on.
Steve
