What is the difference between petrol and diesel fuel?
How does the fuel shut off solenoid work?
What is the four stroke cycle?
What does S.I mean?
What does C.I mean?
When dismantling a carb what precaution should you take?
How does a bimetallic spring work in a automatic choke?
What is the purpose of the venturi and how does it work?
Explain how a fuel cut off solenoid is checked and why is it fitted?
An engine lacks power. What is likely to cause this problem?
How do you adjust the float in a carburettor?
What is the purpose of a power valve?
What are some of the causes of high fuel consumption?
How is the the idle and mixture screw adjusted?
When refitting a three multiple carburettor what should be done after installing them?
Petrol:
Petroleum is a mixture of a very large number of different hydrocarbons; the most commonly found molecules are alkanes (linear or branched), cycloalkanes, aromatic hydrocarbons, or more complicated chemicals like asphaltenes. Each petroleum variety has a unique mix of molecules, which define its physical and chemical properties, like colour and viscosity.
Image from: http://images.cdn.fotopedia.com/flickr-2889488104-image.jpg
Hydrocarbon- A Hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.
Image from: http://www.lloydminsterheavyoil.com/propane.jpg
Alkanes- Alkanes (also known as paraffins or saturated hydrocarbons) are chemical compounds that consist only of the elements carbon (C) and hydrogen (H)
Image from: http://www.jirvine.co.uk/Chemistry_GCSE/C1A/methane.JPG
Cycloalkanes- Cycloalkanes (also called naphthenes) are types of alkanes which have one or more rings of carbon atoms in the chemical structure of their molecules.
Aromatic hydrocarbon- An Aromatic hydrocarbon or arene is a hydrocarbon characterized by general alternating double and single bonds between carbons.
Image from: http://www.nasa.gov/centers/ames/images/content/135869main_panha.jpg
Asphaltenes- Asphaltenes are molecular substances that are found in crude oil, along with resins, aromatic hydrocarbons, and alkanes.
Image from: http://tigger.uic.edu/~mansoori/Asphaltene.Aggregation.GIF
Info from: http://en.wikipedia.org/wiki/Petroleum#Chemistry, http://en.wikipedia.org/wiki/Hydrocarbon, http://en.wikipedia.org/wiki/Alkane, http://en.wikipedia.org/wiki/Cycloalkane, http://en.wikipedia.org/wiki/Aromatic_hydrocarbon, http://en.wikipedia.org/wiki/Asphaltene
Diesel:
Diesel fuel in general is any liquid fuel used in diesel engines. The most common is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted Petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including, cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes).
Image from: http://static.howstuffworks.com/gif/diesel-2.jpg
Fractional Distillation- Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate.
Image from: http://www.tutorbene.com/cms_images/FRACTIONAL%20DISTILLATION.bmp
Biodiesel- Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel typically made by chemically reacting lipids (e.g., vegetable oil, animal fat (tallow) with an alcohol.
Image from: http://www.seco.cpa.state.tx.us/zzz_re/re_biodiesel_carboncycle.gif
Paraffin- In chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2.
Image from: http://lembex-import-inc.tradenote.net/images/users/000/201/938/products_images/Pure_Liquid_Paraffin.jpg
Naphthalene- Naphthalene is an organic compound with formula C10H8.
Image from: http://upload.wikimedia.org/wikipedia/commons/3/3e/Naphthalene-3D-balls.png
Benzene- Benzene is an organic chemical compound with the molecular formula C6H6. It is sometimes abbreviated Ph–H. Benzene is a colourless and highly flammable liquid with a sweet smell.
Image from: http://zoxovema.comlu.com/gallery/benzene.jpg
Info from: http://en.wikipedia.org/wiki/Diesel_fuel#Chemical_composition, http://en.wikipedia.org/wiki/Paraffin, http://en.wikipedia.org/wiki/Naphthalene, http://en.wikipedia.org/wiki/Alkylbenzene\, http://en.wikipedia.org/wiki/Fractional_distillation
The 4-Stroke cycle:
4-Stroke cycle animation found on YouTube-
S.I engine:
Spark Ignition engine- Petrol operating engine
Video found on you tube
C.I engine:
Compression Ignition engine- Diesel operating engine
Video found on You Tube
Fuel shutoff solenoid-why it’s fitted, how it works, and how it’s checked
A solenoid valve is an electromechanical valve controlled by an electric current. The electric current runs through a solenoid, which is a wire coil wrapped around a metallic core. A solenoid creates a controlled magnetic field when an electrical current is passed through it. This magnetic field affects the state of the solenoid valve, causing the valve to open or close. Fuel shut-off solenoids transport fuel from a machine's gas tank to its engine. A fuel shut-off solenoid is attached to the machine's main electrical system, which can monitor and detect abnormal temperatures or mechanical malfunctions. Should something go wrong, the electrical current running to the solenoid will be interrupted, causing the solenoid valve to close and shutting off the supply of fuel to the engine.
Info from: http://www.ehow.com/how-does_5016171_diesel-fuel-shutoff-solenoids-work.html
Image from: http://cf.mp-cdn.net/63/2e/3f2e8ffd3cf6050ab42cec2cf7f1.jpg
The venturi-The purpose and how it works
When air is drawn down a tube that has a restriction in it like the throat and venturi in the diaphragm, it must speed up as it passes the restriction. As it does so the pressure in the area of the restriction or venturi drops. This drop in pressure is used to draw fuel into the throat of the carburettor. There must be a constant supply of fuel with a level slightly bellow the opening of the discharge tube or nozzle into the venturi. To achieve this, a float chamber is used in which a float and needle valve provide a constant fuel level within the chamber.
Info from: Applied technology & trades-Marine engineering book
Video found on YouTube explaining the venturi effect-
Power valve-It’s purpose
For open throttle operation a richer mixture will produce more power, prevent pre-ignition detonation, and keep the engine cooler. This is usually addressed with a spring-loaded "power valve", which is held shut by engine vacuum. As the throttle opens up, the vacuum decreases and the spring opens the valve to let more fuel into the main circuit. On two-stroke engines, the operation of the power valve is the reverse of normal — it is normally "on" and at a set rpm it is turned "off". It is activated at high rpm to extend the engine's rev range, capitalizing on a two-stroke's tendency to rev higher momentarily when the mixture is lean.
Image from: http://www.bikerumor.com/wp-content/uploads/2009/07/ashima-power-valve-brake.jpg
Info from: http://en.wikipedia.org/wiki/Carburetor#Power_valve
When dismantling a carburettor, you should be aware of small components such as: needle valves used to block and allow fuel/air flow, ball Barings used to allow fuel/air flow. Basically, when taking a carburettor apart, keep components in their assigned group. E.g. When unscrewing bolts from the float bowl/chamber, lie them down in which hole they came out of (e.g: if bolts came from holes on the left of the float bowl, put them next to you in order from top to bottom. Visa versa for opposite side). keep a magnetic pick up close by. If you drop a piece and lose it, buy a new carburettor. You can’t afford to lose a single component/piece of carburettor when taking apart of fixing them. It could result in high fuel consumption and/or cause the engine to run lean or too rich. It is vital not to lose the component on a carburettor, such as the components pointed out bellow.
Image from: https://docs.google.com/present/view?id=df8cgkbk_88cgrtb2fz
Info from my knowledge of carburettor dismantling.
Carburettor problems:
The reasons why an engine lacks power would be that:
. The power valve is stuck closed, or
. The float level is too low, or
. There are restrictions in jets, air bleeds, or passage ways, or
. There is lack of fuel to the carburettor, or
. The air intake has restrictions, or
. The inlet manifold has leaks, or
. The secondary butterfly is not opening properly (dual throat carb), or
. The accelerator cable is not adjusted properly or has faults, or
. The secondary secondary air valve isn't opening properly (dual throat carb).
Info from: Page 9 of TTEC 4234 Fuels and fuel systems-Marine (Fuels practical workbook) book
Alternate causes of high fuel consumption are:
. The choke valve isn’t opening/open properly, or
. The carburettor is flooding, or
. The float level is too high, or
. There is fuel percolation (percolation- concerns the movement and filtering of fluids through porous materials in the bowl), or
Info from: http://en.wikipedia.org/wiki/Percolation
. The air being sucked into the air intake is either too hot or too cold, or
. The air intake has restrictions, or
. The fuel line and/or fittings have leaks, or
. The power valve is stuck open, or
. The link to the accelerator pump is out of adjustment, or
. There are restrictions in the air bleeds or passages.
Info from: Page 11 of TTEC 4234 Fuels and fuel systems-Marine (Fuels practical workbook) book
Adjustment of the idle mixture screw:
The idle and mixture screws are adjusted by either a Philips or flathead screw driver. (Screw heads vary depending on carburettor model).
Info from my knowledge of dismantling carburettors
How the vacuum fuel pump works:
Since the carburettor isn’t manly enough to suck enough fuel into the top of the cylinder head(s), a vacuum pump is fitted in/onto the fuel system. the vacuum pump consists of a diaphragm which uses the stroke/pressure of the pistons to suck fuel into the carb and into the top of the cylinder heads. The pressure you would get from this type of pump would be around 30 to 80 psi of fuel pressure.
Image from: http://continuouswave.com/whaler/reference/images/vro719x632.jpg
Info (edited) from: http://gregtothill.blogspot.com/, http://calvinbayley.blogspot.com/, and http://www.aa1car.com/library/fuel_pump_diagnose.htm
Excellent work, keep it up.
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