Flooded engine

Last updated

A flooded engine is an internal combustion engine that has been fed an excessively rich air-fuel mixture that cannot be ignited. [1] This is caused by the mixture exceeding the upper explosive limit for the particular fuel. An engine in this condition will not start until the excessively rich mixture has been cleared. [2] It is also possible for an engine to stall from a running state due to this condition.

Contents

Condition

Engine flooding was a common problem with carbureted cars, but newer fuel-injected ones are immune to the problem when operating within normal tolerances. Flooding usually occurs during starting, especially under cold conditions or because the accelerator has been pumped. It can also occur during hot starting; high temperatures may cause fuel in the carburetor float chamber to evaporate into the inlet manifold, causing the air/fuel mixture to exceed the upper explosive limit. High temperature fuel may also result in a vapor lock, which is unrelated to flooding but has a similar symptom. Flooding can also occur if the choke has been over applied or has malfunctioned.

A severe form of engine flooding occurs when excessive liquid fuel enters the combustion chamber. This reduces the dead volume of the combustion chamber and thus places a heavy load on the starter motor, such that it fails to turn the engine. Damage (due to excessive compression and even dilution of the lubricating oil with fuel) can also occur. This condition is known as the engine "flooding out." Possible causes of too much liquid fuel in the engine include a defective carburetor float that is not closing the fuel inlet needle valve, or debris caught in the needle valve preventing it from sealing.

Liquids inside an internal combustion engine are extremely detrimental because of the low compressibility of liquids. Although not the most common cause, a severely flooded engine could result in a hydrolock. A hydrolock occurs when a liquid fills a combustion chamber to the point that it is impossible to turn the crankshaft without a catastrophic failure of the engine or one of its vital components.

The conventional remedy for a flooded carbureted engine is to steadily hold the throttle full open (full power position) while continuing to crank the engine. This permits the maximum flow of air through the engine, flushing the overly rich fuel mixture out of the exhaust. If the exhaust system is hot enough to autoignite, an after-fire may result; this can be seen as a flame discharging through the exhaust system. On a fuel-injected engine, ignoring the throttle (no fuel) while starting permits electronic logic systems to produce the correct fuel mixture, often based on exhaust gases. Some fuel injection computers interpret "pumping" the throttle to indicate a flooded engine, and alter the fuel-air mixture accordingly. In a carbureted engine equipped with an accelerator pump (which advances fuel flow to match air ingestion under rapid throttle acceleration), "pumping" the throttle will force excess fuel into the engine, further flooding it.

In worst cases, the excess fuel can foul spark plugs, sometimes necessitating their cleaning or replacement before the engine will start. This is most likely to occur on a carbureted engine in cold weather, after a running engine has been shut off briefly before being restarted. Doing so can cause the choke valve to configure the mixture for a cold engine start, despite higher actual temperatures, resulting in an overly rich mixture and flooded engine.

See also

Related Research Articles

<span class="mw-page-title-main">Carburetor</span> Component of internal combustion engines which mixes air and fuel in a controlled ratio

A carburetor is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances.

<span class="mw-page-title-main">Exhaust gas recirculation</span> NOx reduction technique used in gasoline and diesel engines

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline, diesel engines and some hydrogen engines. EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. The exhaust gas displaces atmospheric air and reduces O2 in the combustion chamber. Reducing the amount of oxygen reduces the amount of fuel that can burn in the cylinder thereby reducing peak in-cylinder temperatures. The actual amount of recirculated exhaust gas varies with the engine operating parameters.

Pre-ignition in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events.

<span class="mw-page-title-main">CVCC</span> Reduced-emissions engine by Honda

CVCC, or Compound Vortex Controlled Combustion, is an internal combustion engine technology developed and trademarked by the Honda Motor Company.

Dieseling or engine run-on is a condition that can occur in spark-plug-ignited, gasoline-powered internal combustion engines, whereby the engine keeps running for a short period after being turned off, drawing fuel through the carburetor, into the engine and igniting it without a spark.

Manifold vacuum, or engine vacuum in a petrol engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.

<span class="mw-page-title-main">Back-fire</span> Explosion in the exhaust of an engine

A backfire or afterburn is combustion or an explosion produced by a running internal combustion engine that occurs in the exhaust system, rather than inside the combustion chamber. It is also sometimes referred to as an afterfire, especially in cases where the word backfire is used to mean a fuel burn that occurs while an intake valve is open, causing the fire to move backward through the system and out through the intake instead of the exhaust. When the flame moves backward it may also be called a "pop-back". A backfire can be caused either by ignition that happens with an exhaust valve open or unburnt fuel making its way into the hot exhaust system. A visible flame may momentarily shoot out of the exhaust pipe. A backfire is often a sign that the engine is improperly tuned.

Vapor lock is a problem caused by liquid fuel changing state to vapor while still in the fuel delivery system of gasoline-fueled internal combustion engines. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult.

Wide open throttle or wide-open throttle (WOT), also called full throttle, is the fully opened state of a throttle on an engine. The term also, by extension, usually refers to the maximum-speed state of running the engine, as the normal result of a fully opened throttle plate/butterfly valve. In an internal combustion engine, this state entails the maximum intake of air and fuel that occurs when the throttle plates inside the carburetor or throttle body are "wide open", providing the least resistance to the incoming air. In the case of an automobile, WOT is when the accelerator is depressed fully, sometimes referred to as "flooring it". A throttle on a steam engine controls how much steam is sent to the cylinders from the boiler.

<span class="mw-page-title-main">Hydrolock</span> Type of hydraulic compression system failure

Hydrolock is an abnormal condition of any device which is designed to compress a gas by mechanically restraining it; most commonly the reciprocating internal combustion engine, the case this article refers to unless otherwise noted. Hydrolock occurs when a volume of liquid greater than the volume of the cylinder at its minimum enters the cylinder. Since liquids are nearly incompressible the piston cannot complete its travel; either the engine must stop rotating or a mechanical failure must occur.

A nitro engine generally refers to an engine powered with a fuel that contains some portion of nitromethane mixed with methanol. Nitromethane is a highly combustible substance that is generally only used in very specifically designed engines found in Top Fuel drag racing and in miniature internal combustion engines in radio control, control line and free flight model aircraft.

In internal combustion engines with carburetors, a choke valve or choke modifies the air pressure in the intake manifold, thereby altering the air–fuel ratio entering the engine. Choke valves are generally used in naturally aspirated engines to supply a richer fuel mixture when starting the engine. Most choke valves in engines are butterfly valves mounted upstream of the carburetor jet to produce a higher partial vacuum, which increases the fuel draw.

Secondary air injection is a vehicle emissions control strategy introduced in 1966, wherein fresh air is injected into the exhaust stream to allow for a fuller secondary combustion of exhaust gases.

A throttle is a mechanism by which fluid flow is managed by construction or obstruction.

The Quadrajet is a four barrel carburetor, made by the Rochester Products Division of General Motors. Its first application was the new-for-1965 Chevy 396ci engine. Its last application was on the 1990 Oldsmobile 307 V8 engine, which was last used in the Cadillac Brougham and full size station wagons made by Chevrolet, Pontiac, Oldsmobile, and Buick.

<span class="mw-page-title-main">Model engine</span>

A model engine is a small internal combustion engine typically used to power a radio-controlled aircraft, radio-controlled car, radio-controlled boat, free flight, control line aircraft, or ground-running tether car model.

A pressure carburetor is a type of fuel metering system manufactured by the Bendix Corporation for piston aircraft engines, starting in the 1940s. It is recognized as an early type of throttle-body fuel injection and was developed to prevent fuel starvation during inverted flight.

<span class="mw-page-title-main">Carbureted compression ignition model engine</span> Type of carbureted engine

A carbureted compression ignition model engine, popularly known as a model diesel engine, is a simple compression ignition engine made for model propulsion, usually model aircraft but also model boats. These are quite similar to the typical glow-plug engine that runs on a mixture of methanol-based fuels with a hot wire filament to provide ignition. Despite their name, their use of compression ignition, and the use of a kerosene fuel that is similar to diesel, model diesels share very little with full-size diesel engines.

<span class="mw-page-title-main">Bendix-Stromberg pressure carburetor</span> Aircraft engine part used by the US in WW2

Of the three types of carburetors used on large, high-performance aircraft engines manufactured in the United States during World War II, the Bendix-Stromberg pressure carburetor was the one most commonly found. The other two carburetor types were manufactured by Chandler Groves and Chandler Evans Control Systems (CECO). Both of these types of carburetors had a relatively large number of internal parts, and in the case of the Holley Carburetor, there were complications in its "variable venturi" design.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance. This process transforms chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

References

  1. ↑ "How to fix a flooded engine | The AA". www.theaa.com. Retrieved 2022-10-10.
  2. ↑ Chase, Kate J. (September 2005). The Savvy Guide to Car Maintenance and Repair. Indy Tech Publishing. p. 135. ISBN   978-0-7906-1321-5.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.