A Body GM Car EVAP System
The EVAP (Evaporative Emission Control) system in a GM A-body car is designed to prevent fuel vapors from escaping into the atmosphere. The system consists of several components, including a fuel tank, a charcoal canister, and a purge valve.
Fuel Tank
The fuel tank is the main storage container for fuel in the vehicle. It is made of a metal or plastic material and is located under the rear of the car. The fuel tank has a vent line that allows air to enter and exit the tank as the fuel level changes.
Charcoal Canister
The charcoal canister is a cylindrical-shaped container that is filled with activated charcoal. The activated charcoal is a highly porous material that absorbs fuel vapors. The canister is connected to the fuel tank vent line and to the purge valve.
Purge Valve
The purge valve is a solenoid-operated valve that controls the flow of fuel vapors from the charcoal canister to the engine. The purge valve is opened when the engine is running and the throttle is open. This allows the fuel vapors to be drawn into the engine and burned.
Operation of the EVAP System
The EVAP system operates in two modes:
* Storage mode: In storage mode, the EVAP system captures fuel vapors from the fuel tank and stores them in the charcoal canister. The purge valve is closed during storage mode.
* Purge mode: In purge mode, the EVAP system releases the fuel vapors from the charcoal canister into the engine. The purge valve is opened during purge mode.
The EVAP system is controlled by the powertrain control module (PCM). The PCM monitors the engine speed, throttle position, and other factors to determine when to switch between storage mode and purge mode.
Troubleshooting the EVAP System
If the EVAP system is not functioning properly, it can cause a number of problems, including:
* Check engine light: The check engine light may come on if the EVAP system is not functioning properly.
* Fuel leaks: Fuel leaks can occur if the EVAP system is not functioning properly.
* Poor fuel economy: Poor fuel economy can occur if the EVAP system is not functioning properly.
If you are experiencing any of these problems, it is important to have the EVAP system diagnosed and repaired by a qualified technician.
EVAP System Maintenance
The EVAP system requires very little maintenance. However, there are a few things you can do to help keep the system functioning properly:
* Keep the fuel tank full: Keeping the fuel tank full will help to prevent fuel vapors from escaping into the atmosphere.
* Avoid overfilling the fuel tank: Overfilling the fuel tank can cause fuel vapors to escape into the atmosphere.
* Have the EVAP system inspected regularly: A qualified technician can inspect the EVAP system and make sure that it is functioning properly.
By following these simple tips, you can help to keep the EVAP system in your GM A-body car functioning properly and prevent fuel vapors from escaping into the atmosphere.
Additional Resources
* [GM A-Body EVAP System Diagram](https://www.gm-trucks.com/forums/topic/205402-a-body-evap-system-diagram/)
* [How to Diagnose and Repair an EVAP System](https://www.youtube.com/watch?v=4-4x6_tU_8A)
* [EVAP System Maintenance Tips](https://www.yourmechanic.com/article/how-to-maintain-your-evap-system-by-jermaine-sims)
