Posts Tagged ‘compression’

07
Oct

What’s The Difference Between Diesel And Gas Engines?

Ken,

Aside from using different types of fuel, what is the real difference between diesel and gas engines?

-Eric Y., WA

Eric,

The main difference between the two types of engines is the method of combustion.  Gas engines use spark plugs to ignite the precombined mixture of air and gasoline.

Diesel engines on the other hand, don’t have spark plugs at all.  Instead, they rely on compression to generate enough heat to cause combustion.  Another difference is that the fuel in diesel engines is not premixed as it is in a carburetor in gas engines.  Instead, the fuel is injected directly into the cylinders while the cylinder is under compression.  This caused the vaporized fuel to burn immediately.

- Ken the Car Guy

05
Oct

How Do I Start A Stored Car?

Ken,

My dad’s car has been in storage for the past 3 years.  I puled it out the other day and tried to get it to start, but nothing happened.  It turns over, but won’t start.  As far as I know, it was working when it was put away.  Where do I start?

-Charlie B., AZ

Charlie,

In this situation, it’s hard to tell exactly what the the problem is, but there are a few things to try.  If there was gas left in the tank when it was stored, it may have evaporated in the tank and carburetor, leaving a gummy residue that can stop the carb from working properly.  Even if the carb isn’t the immediate problem, you’ll want to clean it out anyway, so I’d start there.  Simply disconnect it and flush it out with tons of carb cleaner.

After reconnecting the carb, if the engine still won’t fire, I’d check the compression and spark plugs.  Spark plugs are cheap, so you can begin by replacing the old ones.  To test the compression, turn over the engine by hand with a wrench.  If there’s resistance at regular intervals your compression is good.  If not, the engine will need some professional work.

- Ken the Car Guy

10
Sep

What Is Brake Fluid?

Ken,

What is brake fluid exactly?  Is there any reason why I can’t refill my fluid with water?

-Graham B., MI

Graham,

There are several things about brake fluid that make it better than water.  Water will work just fine for a while, but brake fluid contains corrosion inhibitors which will keep your brakes from rusting in the presence of water.

Brake fluid also doesn’t expand or contract as much as water in the cold or heat.  This feature keeps your brakes from seizing if the temperature suddenly changes.

Another good thing about brake fluid is that it has a higher boiling point, at 500 degrees Fahrenheit.  If you were to use plain water instead, the brakes may get hot enough to flash boil the water which would certainly cause you many more problems.

As I said earlier, water can get you by in a pinch; if you need to drive to the auto store for more brake fluid for example, but don’t use it for very long as it can have damaging effects on your vehicle.

- Ken the Car Guy

15
Aug

What Is A Compression Test?

Ken,

My mechanic tells me I need a compression test, but I neglected to ask him what that is exactly.  Can you help me out?

- Roberto O., NV

Roberto,

A compression test will check your engine for pressure leaks.  Good compression is important in an engine because leaks can cause pistons to misfire which leads to poor performance.

Compression is especially important in diesel engines because they don’t use spark plugs.  Instead of using a spark to ignite the fuel, diesels compress the combination of fuel and oxygen so much that the temperature skyrockets, causing combustion.  Poor compression in a diesel can easily lead to engine failure.

Compression tests are good to do routinely, they don’t cost much and they let you know the state of your engine.  If one of your cylinders is misfiring, this test can help you determine the reason why.

- Ken the Car Guy