Which symptom indicates an aneroid device has been shorted on a hydromechanical diesel engine?

Which symptom indicates an aneroid device has been shorted on a hydromechanical diesel engine?

• A. Increased top end power
• B. Improved lug performance
• C. Smoking at rated speed and load
• D. Puff of exhaust smoke at each upshift

Answer: (D)

The diagnostic idea here is that the aneroid device is part of the hydromechanical governor and helps trim fuel delivery as the engine load and air flow change. If the aneroid capsule is shorted, it can’t respond correctly during quick changes in load, such as when you upshift. As gear is changed, the engine expects a momentary adjustment in fuel, but the shorted aneroid fails to back off fuel appropriately, so extra fuel is injected for a brief instant. That transient overfuel shows up as a puff of exhaust smoke with each upshift. The other options don’t match this shift-specific, transient behavior—they would imply a more constant change in performance rather than a repeatable smoking puff tied to shifting.

The diagnostic idea here is that the aneroid device is part of the hydromechanical governor and helps trim fuel delivery as the engine load and air flow change. If the aneroid capsule is shorted, it can’t respond correctly during quick changes in load, such as when you upshift. As gear is changed, the engine expects a momentary adjustment in fuel, but the shorted aneroid fails to back off fuel appropriately, so extra fuel is injected for a brief instant. That transient overfuel shows up as a puff of exhaust smoke with each upshift. The other options don’t match this shift-specific, transient behavior—they would imply a more constant change in performance rather than a repeatable smoking puff tied to shifting.