The 8 Best Timing Lights
This wiki has been updated 19 times since it was first published in February of 2016. If you want to make sure your vehicle is running as efficiently as possible, you'll need to check the timing of the spark in relation to the piston with one of these lights. We've included budget-friendly models good for home or occasional use through to professional-grade units that can stand up to the rigors of a busy automotive shop. When users buy our independently chosen editorial selections, we may earn commissions to help fund the Wiki. Skip to the best timing light on Amazon.
Air, Fuel, and Spark
In fact, cars have been scooting down the road for decades now thanks to millions of little, tiny, violent explosions happening in quick succession.
No, they're not a 1970s soul band, but they are on fire. Or, more accurately, you could say that together they cause fire. And if that fire happens under enough pressure, there'll be a violent explosion — and who doesn't love (safe and controlled) explosions?
Cars certainly love them. In fact, cars have been scooting down the road for decades now thanks to millions of little, tiny, violent explosions happening in quick succession. They comprise the most energetic part of the internal combustion engine: the combustion itself.
But cars are big machines. If those little explosions pack enough punch to hurtle a two-ton vehicle down the road at 85 mph, there must be a pretty exact science to making sure that each of these ingredients is applied in the proper volume and at the exactly right time.
Fear not, because engineers have developed an intricate system of air/fuel/spark timing, ensuring that our trusty engine is getting its gasoline and oxygen meals at precisely the right intervals.
Don't Let The Mechanic Get The Best Of You
Sometimes, cars run strangely. Sometimes, they have rough idles or get choppy during a certain range of RPM. Other times, enthusiasts create customized vehicles, complete with specialized, high-performance engines. In all of these cases, it's absolutely worth making sure that your engine's timing is properly set, and a mechanic will charge you a minimum of $100 simply to offer a diagnosis. And that doesn't include labor. But timing is one test you don't necessarily need to have done at the shop. A simple and readily available tool, the timing light can enable you to check this integral setting on your vehicle from your very own one-car garage.
Other times, enthusiasts create customized vehicles, complete with specialized, high-performance engines.
Let's slow down a bit, though. Opening the hood and inserting strange, flashing gadgets into the engine compartment can seem intimidating at first, especiaally to the non-gearhead. Don't worry; this isn't an involved process. It's worlds easier than, for example, a brake job. And just a couple more steps (again, relatively simple) let you adjust your engine's timing, making sure you don't have to take an extra, expensive trip to the automobile doctor just to address that cylinder that keeps knocking or misfiring at 4,000 RPM. Of course, to understand and adjust timing, it helps to have at least a fundamental knowledge of how an internal combustion engine works. While they look like big, complicated beasts, engines actually aren't so difficult to understand on a basic level.
As mentioned earlier, combustion happens in the presence of three things: oxygen, a fuel source, and a spark. In standard engines, this happens inside cylinders bored into the solid metal of the engine block. To start the process, the crankshaft pulls the piston away from the cylinder head, essentially the base of operations for combustion. Valves in the cylinder head open to allow air into the now voluminous cylinder while the fuel injectors spray a measured amount of gasoline or the mechanical carburation allows air-fed gasoline into the cylinder at a set rate. When the piston is at its peak distance from the cylinder head, the camshaft (a knurled rod, or sometimes two, running parallel to the crankshaft) lets the valves close. The piston then compresses the space, and the spark plug fires after the air/fuel mixture has been increased to as much as eleven times atmospheric pressure. Then, BOOM.
This fire under pressure, also known as an explosion, forces the piston outward. The piston rods propel the crank to rotate, the crank turns the flywheel, and then the motor's job is done and the transmission takes over.
The Miracle's In The Timing
The kicker here is that, because the power plant of a car is made of so many complex moving parts, the camshaft, crankshaft, fuel injectors, and spark aren't permanently connected in a fixed system. In reality, they operate as a series of components that manipulate each other mechanically, and some of these components can independently move slightly out of alignment. This throws the whole system out of whack. For that reason, cars are most often designed with one particular belt (or rarely, a chain) that attaches to every critically-timed part in the system at once, ensuring that every mechanical voice in the engine is at the same tempo for the entire symphony.
This plug fires when the piston reaches the maximum distance from the crankshaft, a position known as top dead center.
Sometimes, the timing belt is prominent in the motor, and in some setups, it must be removed before certain large jobs are done to the car or frame. It's commonly found underneath a few engine components. Because it's such an important part, most manufacturers recommend it be replaced every 60,000-100,000 miles. If a timing belt should break during use, the best-case scenario is that your car simply won't run until it's replaced. If a car uses an interference engine, meaning the pistons and valves occupy the same physical space in the combustion chamber but at different times in the firing process, a popped timing belt could very well destroy an engine beyond repair. Interference motors are very common, so it's important to give timing belts their proper due.
Using a timing light is actually very easy. Check your car's manual to learn which of the pulleys has the timing marks around it. Connect the light to your battery and clamp its signal wire to the number one spark plug. This plug fires when the piston reaches the maximum distance from the crankshaft, a position known as top dead center. When the timing light is aimed correctly, exact degree markings will become visible on the pulley, telling you how far advanced or retarded your engine's timing is relative to TDC. The distributor is easily adjusted to bring this figure in line with your car's specifications.
Remember, any dirty hands or cut knuckles you experience are a small price to pay for not getting fleeced by a mechanic.
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