Vapor lock

[aquadave]

I feel really old. My brother was having vapor lock problems with his 84 Harley. Being familiar with vapor lock I knew right off what it was. I did a look on some HD forums to see if there was anything special about HD's vapor locking. Wow, I read so much crap, like There have been no reported cases of vapor lock since 71 in any vehicles (this includes cars). Clean the vent tube, and I've never seen it but heard of it. Apparently I've had all the vapor lock issues more than the entire internet.

Let's start with the easy one Hydro lock that's when there is no ventilation on the tank to allow gas to flow to the carb or efi. Basically like putting your finger over a straw to hold water in it. Symptoms You pretty much run out of gas. High or low speeds hot or cold weather. Break the vacuum and you go again

Vapor lock Is the gas vaporizes in the fuel line, causing pressure not allowing fuel to flow in the carb. symptoms It mostly happens during HOT weather, Low speed to idle, acts like it ran out of gas the engine can even knock like the bearings are bad, and can shut down. After it shuts down it can act like a dead batt trying to start. let it sit and fires right up. How do you fix it? Old timey ways to increase fuel tube dia or use a cool can. My favorite and it really works clamp wooden clothes pins on the fuel line. Also you can use a high octane gas or put moth balls in the gas tank. Be careful with moth balls they raise the octane high enough to blow your engine, but it's a fun ride until you do. Vapor lock is carbs only not fuel injection

I can tell you for a fact if you have an engine with a carb you can vapor lock no matter what you read. So if you remember the symptoms you can save a lot of money on repairs when really nothing was wrong. increase octane and wooden clothes pins

[satchick]

Hydro lock that's when there is no ventilation on the tank to allow gas to flow to the carb or efi

I always thought (and had been told) that hydrolock was when the cylinder itself was full of liquid, either oil, fuel, coolant.... Since liquids don't compress this can lock up the engine, or throw a rod through the block if it happens with the engine running (major head gasket failure dumping coolant into a cylinder).

[hutch]

I used to have vapor lock problems a lot with chain saws. One needs to be careful. Opening the cap when the gas is boiling causes fires. Once I threw one in a swimming pool to put it out.

[BHill]

I always thought (and had been told) that hydrolock was when the cylinder itself was full of liquid, either oil, fuel, coolant.... Since liquids don't compress this can lock up the engine, or throw a rod through the block if it happens with the engine running (major head gasket failure dumping coolant into a cylinder).

You are right satchick that is what it's called.

[BHill]

Just a little info about fuels and octanes.

C/P
How to decide which grade of gas is right


Costa Mouzouris
SPECIAL TO THE STAR

If you’re like many drivers, you may have been unwittingly nudged into thinking that using a higher-octane fuel than recommended will give you better performance.
A common misconception about octane is its relation to power output, and many people believe that the higher the octane the more power the fuel will produce.
It’s an understandable mistake, as oil companies have been associating premium blends with high horsepower for decades. It’s in their interest to do so, after all, because ‘premium’ fuel demands a premium price.
However, the grade of gas you put into your tank is entirely dependent on the type of engine you have in your vehicle, and if you don’t have a high-compression engine, then adding premium gas not only puts more money into the pockets of the gas companies, it may even be detrimental to performance.
With current unrest in the Middle East already affecting pump prices, you’ll want to look at what factors define what grade of gas you need to use. It might save you money.
For starters, let’s take a look at what happens inside your engine. If you know your physics, you know that the more you compress a gas the more heat it generates. This also occurs when a fuel mixture is compressed inside your engine by the rising piston, as it moves a relatively large volume of air and fuel into a very small space prior to ignition: the smaller the relative space, the higher the compression ratio.
As air and gasoline molecules are squeezed together when compressed, they enable a quicker and more complete burn, so the higher the effective compression, the more energy that can be released from a given quantity of fuel.
This, in turn, boosts power output, which is why high-performance engines are synonymous with high compression ratios.
In practice, a spark plug ignites the mixture and produces a flame front that works its way through the combustion chamber. Ignition isn’t an explosion, but rather a controlled burn.
A spark plug is timed to fire early enough so that combustion reaches peak pressure just as the piston begins its downward power stroke, thus maximizing the efficiency of the burn.
But if a mixture is compressed enough (generating a lot of heat), and combines with the ambient heat produced by the engine, it can self-ignite elsewhere in the combustion chamber, thus producing two flame fronts, which have the effect of amplifying the resulting pressure waves.
These pressure waves pound against the combustion chamber and cause a condition known as engine knock, or detonation; a metallic pinging noise that can be likened to rattling a couple of steel balls in a steel can.
The problem with detonation is that it causes peak pressure to generate before it’s supposed to, which pushes on the piston too soon and effectively tries to turn the engine backwards. It’s only the momentum of the crankshaft that keeps it from doing so, but the result is increased combustion chamber heat (further increasing the potential for detonation), power loss and potential engine damage.
Although a major contributing factor, compression ratio alone does not determine an engine’s tendency to knock. Another factor is cylinder bore.
Larger bores require more time for the flame front to burn throughout the combustion chamber, thus allowing more time for the fuel mixture to self-ignite and cause detonation. This is why larger-bore engines generally have lower compression ratios.
Another factor is cam timing. Aggressive cam timing reduces the effective compression ratio: the longer the intake valves stay open, the later the piston begins compressing the mixture on its way back up the cylinder. This is why high-performance engines can get away with higher compression ratios.
Finally, there’s elevation. The higher up into the atmosphere you live, the less dense the air is, therefore the less air there is to compress, generating less heat and reducing the risk of detonation.
Detonation is not be confused with pre-ignition, which is the result of high-heat areas in the combustion chamber, like heated carbon deposits, that ignite the fuel before the spark plug fires. Sustained detonation or pre-ignition can lead to serious engine damage.
Your first line of defence towards warding off detonation is in the gasoline. Gasoline contains one or more additives that inhibit its ability to detonate (it used to be tetra-ethyl lead, but that has now been replaced with less toxic chemicals, including ethanol).
A gasoline’s resistance to detonation is indicated by its octane rating and there are three different measurements for obtaining octane numbers.
The Research Octane Number (RON) is achieved by simulating light loads, like city driving or highway cruising, and provides the highest octane number.
The Motor Octane Number (MON) simulates extreme conditions, like hard acceleration or driving uphill, and provides the lowest number.
The Anti-Knock Index (AKI) is an average of those two and is what you see displayed as (R+M)/2 at the pump.
Typical AKI grades that you’ll find at the pump are regular at 87, midgrade at 89 and premium at 91. Gas stations blend low- and high-octane fuels at the pump to achieve midgrade blends.
Many engines today use knock sensors to detect detonation and combat it by retarding the ignition timing. It is these engines that are most likely to see a drop in performance if a lower-than-recommended fuel is used, as retarding the timing also reduces power. Using the recommended high-octane fuel in these engines reduces detonation, which allows the timing to run at maximum advance and restores power.
Now here’s where a high-octane fuel can be detrimental to performance. To achieve a high-octane rating, the maximum allowable percentage of ethanol may be blended into fuel, or up to 10 per cent by volume. Ethanol has very good anti-knock properties, so it is used to raise the octane number, but it also lowers gasoline’s energy content.
According to Natural Resources Canada, gasoline with a 10 per cent ethanol blend contains about 97 percent of the energy of pure gasoline. This not only reduces power, but it can also increase fuel consumption by two to three per cent.
So, the main reason manufacturers recommend high-octane fuel in high-performance vehicles isn’t because the fuel has more energy content, it’s to prevent knocking, pure and simple. There’s no advantage to using a higher-octane fuel than that recommended by the manufacturer in a vehicle that doesn’t require it.
The exception is that if you own an older vehicle, the recommended fuel may no longer be effective at preventing knock due to excessive carbon build-up and a lack of modern anti-knock devices, so if you hear that characteristic rattling, fill up with a higher grade at your next fuel stop.
Choose your fuel wisely and save your money. Gasoline prices are on the way up, after all, and you’ll want to get the biggest bang for your buck.

[satchick]

Now here’s where a high-octane fuel can be detrimental to performance. To achieve a high-octane rating, the maximum allowable percentage of ethanol may be blended into fuel, or up to 10 per cent by volume. Ethanol has very good anti-knock properties, so it is used to raise the octane number, but it also lowers gasoline’s energy content.

In my area, high octane fuel is alcohol-free, and only the regular and midgrade are blended with 10% ethanol. I think the 91 at Petro-Canada may have alcohol, but the 94 is definitely alcohol free. I only use 94 in my jetski, for performance reasons, and because ethanol blends will damage fuel system parts. This is the situation for many boats with rubber fuel lines or seals.

[aquadave]

Bhill is right, higher octane will not improve performance if your engine is tuned to run on lower octane, but running lower octane when your engine is tuned to run on high octane will do damage.
Hydro-lock is a vacuum lock, if you have a cylinder filled with water,oil or gas, it's called Fxxxxd Up
The thing about ethanol is it helps run water through your engine. Alcohol and water mix, gas and alcohol mix this allows the gas company to supersaturate water in the gas to smooth out the burn and up profits by watering down gas