Vapor lock what is

Freebase 0. Matched Categories Blockage. How to pronounce vapor lock? Alex US English. David US English. Mark US English. Daniel British. Libby British. Mia British. Karen Australian. Hayley Australian. Natasha Australian. Veena Indian. So this new fuel has a lower boiling point. However, vapor lock rarely occurs in a modern engine because of the use of an in-tank, electric fuel pump.

This allows the pump to operate at a low point in the tank, submerged in fuel, and under a lower temperature than the older mechanical pump located in the engine compartment. Also, in a modern fuel delivery system fuel is pressurized. Furthermore, modern engines are equipped with an electric cooling fan, making it even harder for vapor bubbles to form in the fuel lines under high ambient or operating temperatures. In contrast, most carbureted engines use a mechanical fuel pump to pull fuel out of the tank to feed the engine.

This creates a vacuum in the fuel line lower atmospheric pressure that makes fuel more prone to vaporization under engine high temperatures. Besides, this mechanical fuel pump sits next to the engine, allowing hot ambient, underhood and engine temperatures usually above F or The heat vaporizes the nonpressurized fuel in the line or carburetor.

This vapor expands and creates bubbles that displace fuel, reducing or preventing flow altogether, creating vapor lock and causing the engine to run lean. Still, a modern fuel-injected system can suffer from vapor lock, not only if pressure in the fuel line drops faulty fuel pressure regulator or fuel pump, for example and the fuel line is subjected to high temperatures, but also modern engines that may reach between and F and C using ethanol blended fuels.

High-altitude geographic areas can contribute to vapor lock as well by lowering the fuel boiling point. Have an assistant crank the engine while conducting the test. Photo courtesy of Sumeet Jain on Flickr. Diagnosing a fuel system for vapor lock problems is not a clear-cut process, but you can search for clues that may point to it.

For example, ask yourself the following questions:. Although rare, a fuel injection system can show the same symptoms if fuel vapor finds its way through the delivery system.

However, similar symptoms can appear when dealing with a faulty ignition coil , ignition control module or fuel pump. In this case, though, you'll notice the same symptoms even in cold weather.

A component with a broken coil or electrical circuit may only need to reach operating temperature to fail. If your engine show these symptoms, try the following test the next time your warmed engine stalls or is hard to start when warm:.

If the engine seems to catch while spraying the starting fluid, there's a good chance the fuel delivery system is vapor locked. An in-line electric fuel pump can prevent vapor lock. Photo courtesy of Rovaco on Flickr. There are several potential solutions to prevent fuel lines from overheating and solve vapor lock issues in a carbureted or, when necessary, in a fuel injected engine.

For example:. To confirm a vapor lock problem, we installed a clear hose from the fuel pump to the carburetor inlet. This allowed us to see the hose filling with fuel, with no air bubbles present.

Once the engine compartment heats up, though, the fuel starts to boil and air bubbles form. In our test, with an ambient temperature of 70 degrees Fahrenheit, the temp of the line reaches just degrees. Unfortunately, modern fuel blends can boil at temps as low as degrees. As you can imagine, under-hood temps get much higher on the street than they did in our test.

There are several ways to solve vapor lock problems, including installing an electric fuel pump or adding a plastic carb spacer. At Prestige Motorsports, our favorite method is to install an Aeromotive in-tank fuel pump and return system. A returnless system, by contrast, will keep fuel in the line and allow it to soak up excess heat. The second reason is that this package will prepare you perfectly to convert to fuel injection in the future. This video shows you the full package installation process, step by step, including using the universal templates to achieve a seamless fit.

There are a few other things you can do to minimize vapor lock. If you want to stick with a mechanical pump, stay away from steel lines, which offer no insulation from heat.

Vapor lock typically starts when you shut down an engine. As you shut down, the heat rises up toward the fuel lines. Without air moving through the cowling, fuel in the lines can start to vaporize. But in some rare cases, vapor lock can occur in flight. The best way to avoid or minimize vapor lock is before it happens.

Once you shut down, open the cowling or oil vents. While this might not eliminate the risk of vapor lock, it can greatly reduce it. Also, if it's possible, point your airplane into the wind. Even a small breeze through your cowl and over the engine can help cool it and reduce the chance of vapor lock.

The only real solution is to push the air bubbles out of the lines by pumping a bunch of fuel through with a boost pump. Unfortunately, there's no specific way to know if you have pushed out all of the vapor from your fuel lines. It just comes with experience.

Start by running your fuel pump for a short amount of time seconds , try to start, and if your engine doesn't fire up, try again. Also, check between starts to see if you're dripping fuel onto the ramp below your engine.