How Much Do You Know About Small Engine Parts?

By: Steven Symes

What does the knock sensor monitor for?

The knock sensor sends voltage signals back to the ECU, which uses those to determine if the timing for the engine needs to be retarded, before damaging pre-detonation occurs.

On some engines that require routine valve adjustments, this part helps speed up the process.

Valve covers are designed to take the hassle out of adjusting valves somewhat regularly. They come off by removing just a few bolts and go back on with similar ease.

You must remove this to get the old oil out of the engine.

Sometimes this can be the hardest part of doing an oil change, if you don't have a wrench that's up to the challenge. You can also use penetrating lubricant on the bolt and let it sit for a little while.

This should provide an accurate reading of how much oil is left in the engine, but you might get your hands a little dirty.

When the engine is turned off, you can use the dipstick to see if the oil is full enough, or if you need to add a quart or two. You'll need a rag or paper towel to clean the dipstick off to get an accurate reading, though.

This is the thing that ignites the air and fuel mixture in the engine.

It's amazing to think the spark plugs in your engine are constantly producing sparks to trigger mini explosions in the cylinders, which then turn the wheels.

What acts as a regulator of when exhaust gases escape the combustion chamber?

Valves open and close passageways. In this case, the valve opens and closes the pathway in the cylinder head that connects to the exhaust manifold.

What ensures the piston won't let any gases escape around the edges once it's in the closed position?

Piston seals are usually made of rubber or a similar substance, so they create an airtight seal that won't let exhaust gases or the air and fuel mix to seep out in the least.

Where does the air temperature sensor sit in a car?

The air temperature sensor gives feedback to the ECU, since this information can affect how much fuel should be sprayed by the injectors. The colder the air, the more oxygen-rich it is.

What is the part that keeps the connecting rod and piston together?

With all the force exerted on the piston and connecting rod each time the air and fuel ignite, the gudgeon pin has to be strong and durable, otherwise the engine would fail quickly.

What regulates exactly how much fuel makes its way into each cylinder?

The fuel injector has an incredibly precise nozzle, so the car's ECU can regulate with precision how much fuel should make its way into the cylinders at any given moment.

What exactly does the crankshaft position sensor monitor?

Sometimes called a crank sensor, this sensor is vital in managing the engine's timing, which is especially important in a variable valve timing setup.

If you find oil in the spark plug tubes, what are you likely going to need to replace?

Just how hard replacing the spark plug tube gaskets is really depends on the engine, just like so many other components.

Besides cosmetics, what's one reason you might replace the engine oil cap?

If you look at the underside of your engine oil cap, there's a rubber or silicone seal that should create a tight seal. If that fails, you could conceivably replace it, but you might find it easier to just buy a new cap.

What does a cold start injector pipe provide?

To help starting the car up when the engine is cold, some designs use a pipe that's triggered by the temperature of the coolant and/or a timer circuit.

What are the two kinds of valve lifters?

You might hear valve lifters referred to as a tappet or lash adjuster, but it's the same thing. Just remember that solid valve lifters need to be adjusted periodically.

Which direction does a valve spring pull the valve?

Most people don't think at all about the valve springs in their engine, even though this part is absolutely essential for proper compression.

What is one thing the idler pulleys do?

Idler pulleys keep the belts that drive the alternator, water pump, power steering pump and AC compressor at the proper tension and moving at the right points around the engine compartment.

When reinstalling the cylinder head bolts, what must you be sure to do?

Not only do you need a torque wrench to tighten the bolts enough, you should always follow the manufacturer's recommendation for the tightening pattern.

What small engine part acts as a gate, regulating the flow of air and fuel into the cylinders?

While the camshaft triggers the motions of the valves, it's the actual valves that either let the gases flow in the engine or sit.

What is the function of the piston ring?

The piston ring is usually made of rubber or a similar substance and it sits in a groove that runs around the sides of the piston, forming an airtight seal that the air/fuel mix and exhaust gases shouldn't flow past.

The water outlet on your engine basically is what simple device?

It might sound simple, but the water outlet on your car's engine is essentially a pipe that connects to the water jacket, letting hot coolant flow out of the engine and toward the rest of the cooling system, namely the radiator.

What actually touches the gudgeon pin in the connecting rod?

The purpose of the connecting rod bushing is to reduce vibrations in the engine, but they're made of a durable metal, so they don't dampen as much as rubber bushings would.

What is the purpose of the camshaft knock pin?

The camshaft knock pin fits on the end of the camshaft. Not only does it hold the camshaft sprocket where it should go, the pin lines up the two parts correctly.

What part is most likely worn if your engine is burning oil?

Replacing valve seals is actually a pretty easy job, but it is a little on the tedious side. If you must pass emissions in your area, doing this will be essential.

If a camshaft seal fails, what will happen?

At the end of the camshafts in a car's cylinder head is a rubber seal, designed to keep the oil inside the engine. Normally these last a long time, but in older engines the seal may fail.

What large part do the main bearings hold in place inside the engine?

Even though they're small, the main bearings have a difficult and critical job, considering the crankshaft is converting the up-and-down forces of the pistons into a rotational force.

Why do most automakers use T-T-Y head bolts?

Not every engine has torque-to-yield head bolts, but just about every automaker uses them when the cylinder head is made of aluminum.

An oil leak at the top of a cylinder head could be coming from which part?

The valve cover is located at the top of the cylinder head, making it a likely source of the leak. Of course, the oil cap is another potential origin.

Each valve spring must be fitted with a keeper and what else?

The valve spring, keeper and retainer work together to create a constant amount of pressure, which snaps the valve closed tightly.

What part directly actuates a rocker arm?

Essentially, a rocker arm is an oscillating lever that's actuated by a pushrod, which is actuated by the lobes on the camshaft.

What's the point of the valve guide bushing?

Engines have plenty of moving parts, and that means vibrations are inevitable. The valve guide is the cylinder that the valve moves back and forth in. This bushing just tries to reduce vibrations created by that movement.

A non-interference engine design means you don't risk damage to what critical small parts if the timing is off?

The valves in a non-interference engine never occupy any space the pistons do, even at different times. That means they're never at risk of colliding, which can damage the pistons as well as the valves.

What wheel with teeth connects directly to the crankshaft?

Sometimes called the harmonic balance wheel or crankshaft sheave, is an essential part of the engine's timing system.

What are the uneven sections on the camshafts called?

Camshafts aren't perfectly straight shafts, otherwise the engine wouldn't run properly. They contain uneven lobes that determine when, how much and for how long the valves open.

What part helps the ECU know how much oxygen is contained in each cubic inch of air as it flows into the cylinders?

The air temperature sensor sits in the air intake, gathering data that helps the ECU measure how much gas should be injected into the cylinders. The colder the air, the more oxygen atoms in each cubic inch of it.

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About This Quiz

Get out your magnifying glass and try to remember detail engine schematics. The tiny parts in engines abound! You might think of engines as large, smelly, loud objects sitting under your car hood, but some of the parts are actually very tiny.

When engines were first created, they were relatively simple machines that people marveled at. The fact is, they were loud, smelly, unreliable, weak, and wouldn't last long. That's far different from the engines we get in cars today. We've become conditioned to expect most engines to last the life of a vehicle, thanks to all kinds of innovations in their design. 

Of course, with all that innovation comes complexity. Modern engines contain hundreds of parts, but as a trade-off they are light years ahead of early car engines. If you've ever rebuilt a newer engine, particularly one with fuel injection, you know just how many little components are inside them. Forgetting to install just one little part, or not installing it exactly as you should can result in serious engine problems. Every last component in an engine is important, even the small things you might think are somewhat expendable. 

Just how much do you know about the little things in an engine? Take this quiz to find out! 

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