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Introduction

Use this guide to identify the main parts of a gasoline engine before diagnosing or repairing it. A gasoline engine changes the chemical energy stored in fuel into motion. This guide organizes the engine into fixed parts, moving parts, internal components, and external belt-driven components so you can understand what you're looking at before starting deeper repair work.

What you need

1. Step 1 Prepare the engine safely
  
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  Park the vehicle on a level surface, turn off the engine, set the parking brake, and remove the key.
  
  Let the engine cool before touching any part of it.
  
  Put on safety glasses and work gloves.
  
  Use a wrench to disconnect the negative battery cable before touching belts, the alternator, the water pump, the cooling fan, or electrical connectors.
  
  Never run the engine in an enclosed area; exhaust can kill you.
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2. Step 2 Understand the engine job
  
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  Treat the gasoline engine as a system that changes chemical energy in fuel into motion.
  
  Gasoline or other fuel stores the chemical energy the engine uses.
  
  Use this idea to trace a problem from fuel energy, to internal movement, to the parts driven outside the engine.
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3. Step 3 Sort parts into groups
  
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  Divide engine parts into fixed parts and moving parts before identifying them.
  
  Fixed parts stay mounted and support or contain the moving parts.
  
  Moving parts rotate or slide while the engine runs.
  
  Use these two groups to make the engine layout easier to understand.
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4. Step 4 Identify fixed engine parts
  
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  Look for the stationary engine structure before looking for rotating or sliding parts.
  
  Identify the cylinder block as the main fixed body of the engine.
  
  Identify the cylinders as the fixed bores inside the block where the pistons move.
  
  Keep fingers and tools out of open cylinders and ports so debris doesn't fall into the engine.
  
  Use the fixed part group as the reference point for locating the moving parts.
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5. Step 5 Identify moving internal parts
  
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  Identify the pistons as the parts that move inside the cylinders.
  
  Identify the crankshaft as the rotating shaft linked to piston movement.
  
  Identify the camshaft as the shaft that operates the valve timing parts.
  
  Identify the valves as the parts that open and close during engine operation.
  
  Don't rotate or crank the engine while hands, tools, or loose clothing are near moving parts.
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6. Step 6 Identify external driven parts
  
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  Follow the external belt around the front of the engine.
  
  Identify the alternator as a belt-driven component.
  
  Identify the water pump as a belt-driven component when it is driven by the external belt.
  
  Identify the cooling fan as part of the cooling system shown with the external engine components.
  
  Some engines use different belt paths or fan layouts, so confirm the exact layout before removal.
  
  Keep hands and clothing away from the belt and fan area, even when the engine is off.
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7. Step 7 Plan the repair area
  
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  Choose the repair area by matching the symptom to a component group.
  
  Use the fixed group for issues involving the block, cylinders, housings, or mounting structure.
  
  Use the moving group for issues involving pistons, the crankshaft, the camshaft, or valves.
  
  Use the external group for issues involving the belt, alternator, water pump, or cooling fan.
  
  Stop disassembly if the component layout doesn't match the engine you're working on.
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Conclusion

Use this component map as a starting point before diagnosing or disassembling a gasoline engine. Confirm the exact layout for the engine you're working on, because belt routing and component placement can vary. Repair didn't go as planned? Ask our Answers community for help.

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