1. Listen for unusual noises:
* While the engine is running: Listen carefully for a loud whining, squealing, or rattling sound coming from the area of the smog pump (usually located near the passenger side of the engine). This often indicates bearing failure or internal damage.
2. Check for leaks:
* Visual Inspection: Carefully examine the smog pump and its associated hoses for any cracks, leaks, or loose connections. Look for oil leaks around the pump itself which indicates a seal failure.
* Pressure Test (Advanced): If you have the tools and experience, you can use a pressure gauge to check for leaks in the system. This requires disconnecting and plugging certain lines while pressurizing the system. This is not recommended unless you're comfortable working with automotive vacuum and pressure systems.
3. Inspect the belt:
* Condition: A worn or broken belt can prevent the pump from functioning, resulting in some of the symptoms described below.
4. Observe the engine's performance: This is the trickiest part as symptoms are often indirect:
* Poor performance/Lack of power: A functioning smog pump only marginally impacts performance, so this is not a reliable indicator. If you're experiencing significant power loss, other issues are likely at play.
* Increased emissions: A faulty smog pump will contribute to *slightly* higher emissions, but it's not a dramatic change and you'd need an emissions test to confirm. This is usually not the primary symptom.
* Check Engine Light (If equipped): 1979 trucks likely didn't have an OBD system with a check engine light.
5. The "Wiggle Test" (Limited usefulness):
* Gently try to wiggle the pulley on the smog pump. Excessive play indicates a worn bearing, but this is not definitive.
In short: Unless you hear a clearly identifiable mechanical problem (whining, rattling), diagnosing a bad smog pump by symptoms alone is difficult. The most reliable method is to:
* Visually inspect the pump and related components for damage or leaks. This is your best bet.
* Check the belt for wear.
* If all else fails, consider disconnecting the smog pump's belt. This is a temporary workaround to see if the noises or symptoms change, but not recommended for long term use (due to increased emissions and possible legal consequences).
Important Considerations:
* Emission Regulations: Removing or disabling the smog pump might be illegal in your area, so be aware of local regulations before doing so.
* Mechanic's Expertise: If you're unsure, it's best to consult a mechanic experienced with older vehicles. They can properly diagnose the issue and advise you on the best course of action.
The smog pump is a relatively simple device, but its failure often presents as vague symptoms that are easily confused with other problems. Thorough visual inspection is your best starting point.
