TextUnderstanding the intricate components of fuel systems can be daunting, especially with the wide array of specialized parts like carburetors, mixers, fuel metering devices, LPG regulators, fuel shut-offs, lockoffs, adapters, and fuel injectors. This comprehensive glossary will demystify these essential elements, providing clear definitions and insights into their functions and applications. Whether you’re an industry professional or an enthusiast, this guide will enhance your knowledge and appreciation of these crucial components.
(diagram)
Air Valve Vacuum (AVV): The vacuum signal taken from below the air valve assembly and above the throttle butterfly valve.
ADP: Adaptive Digital Processor.
Air/Fuel Ratio: The amount or balance of air and fuel in the air/fuel mixture that enters the engine.
Analog Voltmeter: A meter that uses a mechanical needle to point to a value on a scale of numbers. It is usually of the low impedance type and used to measure voltage and resistance.
Aromatics: Pertaining to or containing the six- carbon ring characteristic of the benzene series. Found in many petroleum distillates.
Backfire: Combustion of the air/fuel mixture in the intake or exhaust manifolds. A backfire can occur if the intake or exhaust valves are open when there is a mistimed ignition spark.
Benzene: An aromatic (C6H6). Sometimes blended with gasoline to improve anti-knock value. Benzene is toxic and suspected of causing cancer.
Bi-Fueled: A vehicle equipped to run on two fuels. Blow-By: Gases formed by the combustion of fuel and air, which ordinarily should exert pressure only against the piston crown and first compression ring. When rings do not seal, these gases escape or “blow by” the side of the piston into the crankcase.
BTU: British Thermal Unit. A measurement of the amount of heat required to raise the temperature of 1lb. of water 1 degree F.
Butane: An odorless, colorless gas, C4H10 found in Natural Gas and petroleum. One of the five LP gases.
CAFE: Corporate Average Fuel Economy.
CARB: California Air Resources Board.
Carbon Monoxide (CO): A chemical compound of a highly toxic gas that is both odorless and colorless.
Carburetor: An apparatus for supplying an internal- combustion engine a mixture of vaporized fuel and air. In this catalog, a “carburetor” includes both a mixer and throttle body.
Cathode Ray Tube: A vacuum tube in which cathode rays usually in the form of a slender beam are projected on a fluorescent screen and produce a luminous spot.
Circuit: A path of conductors through which electricity flows.
Closed Loop Operation: Applies to systems utilizing an oxygen sensor. In this mode of operation, the system uses oxygen sensor information to determine air/fuel ratio. Adjustments are made accordingly and checked by comparing the new oxygen sensor to previous signals. No stored information is used.
CNG: Compressed Natural Gas. CKP: Crankshaft Position Sensor CMP: Camshaft Position Sensor CNG: Compressed Natural Gas
Conductor: A material, normally metallic, that permits easy passage of electricity.
Contaminants: Impurities or foreign material present in fuel.
Control Module: One of several informal names for a solid state microcomputer which monitors engine conditions and controls certain engine functions; i.e. air/fuel ratio, injection and ignition time, etc. The formal name and the one used throughout this manual is ECM, or Engine Control Module.
Converter: A LPG fuel system component containing varying stages of fuel pressure regulation combined with a vaporizer.
Cryogen: A refrigerant used to obtain very low temperatures.
Current: The volume or flow of electrons through a conductor. Measured in amperes or amps.
DBW: Drive By Wire
Dedicated Fuel System: A motor fuel system designed to operate on only one fuel type.
DG: Digester Gas
Diaphragm: A thin, flexible membrane that separates two chambers. When the pressure in one chamber is lower than in the other chamber, the diaphragm will move toward the side with the low pressure.
Diaphragm Port: The external port located at the fuel inlet assembly and connected to the vacuum chamber above the air valve diaphragm.
DLC: Data Link Connector. DTC: Diagnostic Trouble Code DST: Diagnostic Scan Tool
DVOM: Digital Volt/ohm Meter. A meter that uses a numerical display in place of a gauge and is usually of the high impedance type.
ECT: Engine Coolant Temperature.
ECM: Electronic Control Module
ECOM: A DLC cable supporting CAN and serial communication with a Spectrum II or III ECM.
EFI: Electronic Fuel Injection. A fuel injection system, which uses a microcomputer (ECM) to determine and control the amount of fuel, required by, and injected into, a particular engine.
EGO: Exhaust Gas Oxygen, used to describe a sensor. Also known as “HEGO” (Heat Exhaust Gas Oxygen) sensor, “O2” or “Oxygen sensor.”
EGR: Exhaust Gas Recirculation.
EPA: Environmental Protection Agency: A regulating agency of the Federal government which, among other duties, establishes and enforces automotive emissions standards.
Ethanol: Grain alcohol (C2H5OH), generally produced by fermenting starch or sugar.
Evaporative Emissions Controls: An automotive emission control system designed to reduce hydrocarbon emissions by trapping evaporated fuel vapors from the fuel system.
Excess Flow Valve: A check valve that is caused to close by the fuel when the flow exceeds a predetermined rate.
FTV: Fuel Trim Valve.
FFV: Flexible Fuel Vehicle.
Firing Line: The portion of an oscilloscope pattern that represents the total amount of voltage being expended through the secondary circuit.
FMVSS: Federal Motor Vehicle Safety Standards.
FPP: Foot Pedal Position Sensor
Fuel Injector: a spring loaded, electromagnetic valve which delivers fuel into the intake manifold, in response to an electrical input from the control module.
Fuel Lock: A solenoid-controlled valve located in the fuel line to stop the flow when the engine stops or the ignition switch is off.
Gasohol: 10 percent ethanol, 90 percent gasoline. Often referred to as E-10.
Gasoline: A motor vehicle fuel that is a complex blend of hydrocarbons and additives. Typical octane level is 89.
GCP: Spectrum III (90-pin) ECM.
Greenhouse Effect: A scientific theory suggesting that carbon dioxide from the burning of fossil fuels is causing the atmosphere to trap heat and cause global warming.
HC: Hydrocarbon. An organic chemical compound.
HD 10: A fuel of not less than 80% liquid volume propane and not more than 10% liquid volume propylene.
HD 5: A fuel of not less than 90% liquid volume propane and not more than 5% liquid volume propylene.
HDV: Heavy Duty Vehicle.
Heavy Ends: A term used to describe the buildup of wax-like impurities that fall out of LPG when vaporized.
HEGO: Heated Exhaust Gas Oxygen, used to describe a sensor. Also known as “EGO” (Exhaust Gas Oxygen sensor), “O2” or “Oxygen sensor.”
Hg: Chemical symbol for the element mercury. Used in reference to a measure of vacuum (inches of Hg).
Histogram: The graphical version of a table which shows what proportion of values fall into specific categories over a specific period of time.
Hydrocarbon: A chemical compound made up of hydrogen and carbon (HC). Gasoline and almost all other fuels are hydrocarbons.
Hydrostatic Relief Valve: A pressure relief device installed in the liquid LPG hose on a LPG fuel system.
IAT: Intake Air Temperature
Ideal Mixture: The air/fuel ratio at which the best compromise of engine performance to exhaust emissions is obtained. Typically 14.7:1.
Ignition Reserve: The difference between available voltage and the required voltage.
ILEV: Inherently Low Emission Vehicle.
IMPCO: Imperial Machine Products Company.
Impedance: A form of opposition of AC electrical current flow (resistance) measured in ohms.
Insulation: A nonconductive material used to cover wires in electrical circuits to prevent the leakage of electricity and to protect the wire from corrosion.
Intercept: An electrical term for a type of splice where the original circuit is interrupted and redirected through another circuit.
ITK: IMPCO Test Kit
Knock: Sound produced when an engine’s air/fuel mixture is ignited by something other than the spark plug, such as a hot spot in the combustion chamber. May be caused by a fuel with an octane rating that is too low and/or incorrect ignition timing. Also called “detonation” or “ping.”
Lambda Sensor: A feedback device, usually located in the exhaust manifold, which detects the amount of oxygen present in exhaust gases in relation to the surrounding atmosphere. (See HEGO).
LDV: Light Duty Vehicle.
Lean Mixture: An air to fuel ratio above the stoichiometric ratio; too much air.
LEV: Low Emission Vehicle.
Limp-in or Limp Home: A mode where the ECM or a component has failed, but the vehicle remains operational although the engine may operate minimally. This term may also describe the drivability characteristics of a failed computer system.
Liquid Petroleum Gas (LPG): A fuel commonly known as propane consisting mostly of propane (C3H8), derived from the liquid components of Natural Gas stripped out before the gas enters the pipeline, and the lightest hydrocarbons produced during petroleum refining. Octane level of LPG is 107.
LPG: Liquified Petroleum Gas.
M85: A blend of gasoline and methanol consisting of 85% methanol and 15% gasoline.
Measurements of Pressure: 1 psi=2.06” Hg (mercury) = 27.72” H2O (water column). At sea level atmospheric pressure is 29.92” Hg.
Methanol: Known as wood alcohol (CH3OH), a light, volatile, flammable alcohol commonly made from Natural Gas.
MIL: Malfunction Indicator Lamp.
Misfire: Failure of the air/fuel mixture to ignite during the power stroke.
Mixer: Fuel introduction device that does not include a throttle plate.
MFI: Multiport Fuel Injection. A fuel injection system that uses one injector per cylinder mounted on the engine to spray fuel near the intake valve area of combustion chamber.
MSV: Manual Shut-Off Valve. Refers to the manually operated valve on the LPG tank.
MTBE: Methyl Tertiary Butyl Ether. Oxygenate add to gasoline to reduce harmful emissions and to improve the octane rating.
Multi-fuel System: A motor fuel system designed to operate on two different fuels, such as LPG and gasoline.
NG: Natural Gas (see Natural Gas)
Natural Gas: A gas formed naturally from buried organic material, composed of a mixture of hydrocarbons, with methane (CH4) being the dominant component.
NGV: Natural Gas Vehicle. NOX: See Oxides of Nitrogen. OBD: On Board Diagnostic
Octane Rating: The measurement of the antiknock value of a motor fuel.
OEM: Original Equipment Manufacturer, the vehicle manufacturer.
Open-Loop: An operational mode during which control module memory information is used to determine air/fuel ratio, injection timing, etc., as opposed to actual oxygen sensor input.
Orifice: A port or passage with a calibrated opening designed to control or limit the amount of flow through it.
Oscilloscope: An instrument that converts voltage and frequency readings into traces on a cathode ray tube (also see Cathode Ray Tube).
Oxides of Nitrogen: Chemical compounds of nitrogen bonded to various amounts of oxygen (NOX). A chief smog forming-agent.
Oxygen Sensor: An automotive fuel system that produces a signal in accordance with the oxygen content of the exhaust gas. (See Lambda Sensor).
Oxygenate: Oxygenates (such as MTBE, ethanol and methanol) added to gasoline to increase the oxygen content and therefore reduce exhaust emissions.
Ozone: A radical oxygen module (O3) that is found in the upper atmosphere and filters out ultraviolet radiation from the sun. Ground level ozone is formed by NOX, during the formation of photochemical smog.
Particulates: Microscopic pieces of solid or liquid substances such as lead and carbon that are discharged into the atmosphere by internal combustion engines.
Positive Crankcase Ventilation (PCV): An automotive emission control system designed to reduce hydrocarbon emissions by routing crankcase fumes into the intake manifold rather than to the atmosphere.
Power Derate: A mode of reduced engine power output for the purposes of protecting engine components during a failure or malfunction.
Pressure Differential: The differential between atmospheric pressure and intake manifold (referred to as vacuum) pressure.
Pressure Regulator: A device to control the pressure of fuel delivered to the fuel injector(s).
Primary Circuit: The low-voltage or input side of the ignition coil.
Propane: An odorless and colorless gas, C3H8, found in Natural Gas and petroleum.
psiA: pounds per square inch absolute.
PTV: Pressure Trim Valve
Reactivity: Refers to the tendency of an HC in the presence of NOX and sunlight to cause a smog- forming reaction. The lighter the HC, the lower reactivity tends to be.
Regulator: An assembly used to reduce and control the pressure of a liquid or vapor.
Resistance: The opposition to the flow of current in an electrical circuit. Measured in ohms.
Rest Pressure: Fuel pressure maintained within the system after engine shutdown.
Rich Mixture: An air to fuel ratio below the stoichiometric ratio; too much fuel.
SAE: Society of Automotive Engineers.
Secondary Circuit: The high-voltage output side of the ignition coil.
SEFI or SFI: Sequential Electronic Fuel Injection or Sequential Fuel Injection.
Sensors: Devices that provide the control module with engine information as needed to properly control engine function.
Spark Line: The portion of an oscilloscope pattern that represents the time during which the air/fuel mixture is being burned in the combustion chamber.
Splice: An electrical term for the joining of two or more conductors at a single point.
Stoichiometric Ratio: An ideal fuel/air ratio for combustion in which all of the fuel and most of the oxygen will be burned.
Sulfur Oxides: Chemical compounds where sulfur is bonded to oxygen produced by the combustion of gasoline or any other fuel that contains sulfur. As sulfur oxides combine with water in the atmosphere to form sulfuric acid.
System Pressure: The fuel pressure maintained in the system during normal engine operation.
Tap: An electrical term for a type of splice where the original circuit is not interrupted.
TBI: Throttle Body Injection. Any of several injection systems that have the fuel injector(s) mounted in a centrally located throttle body.
Throttle Body: Controls engine RPM by adjusting the engine manifold vacuum to the mixer. Consists of a housing shaft, throttle liner and butterfly valve.
TLEV: Transitional Low Emission Vehicle.
TMAP: Combined Air Inlet and Manifold Pressure Sensor.
Toluene: A liquid aromatic hydrocarbon C7H8.
TPS: Throttle Position Sensor. TSB: Technical Service Bulletin. ULEV: Ultra Low Emission Vehicle.
USB: Universal Serial Bus. A plug or interface supplied on most personal computers.
Vaporizer: A device that transfers heat to liquid LPG, causing it to vaporize into LPG vapor. Many IMPCO regulators perform this function and are often referred to as converters.
Vaporization: A process in which liquid changes states into gas.
Venturi Air Valve Vacuum (VAVV): An amplified air valve vacuum signal coming from the venturi area of the mixer, directly exposed to airflow before the addition of vaporized LPG.
Volt/ohmmeter: (VOM): A combination meter used to measure voltage and resistance in an electrical circuit. Available in both analog and digital types. May also referred to as AVOM and DVOM.
Voltage: The electrical pressure that causes current to flow in a circuit. Measured in volts.
Voltage Drop: A lowering of the voltage in a circuit when resistance or electrical load is added.
VSS: Vehicle Speed Sensor
w.c.: Water Column. A unit of pressure (measured in inches)
Xylene: C6H4 (CH3)2. Any of three toxic, flammable, and oily isomeric aromatic hydrocarbons that are dimethyl homologues of benzene and usually obtained from petroleum or Natural Gas distillates.
ZEV: Zero Emission Vehicle.
Looking for replacement parts or a new fuel system for your forklift? Intella Parts carries the entire line of IMPCO products,, the leading manufacturer of fuel systems.
ZEV: Zero Emission Vehicle.
Looking for replacement parts or a new fuel system for your forklift? Intella Parts carries the entire line of IMPCO products, the leading manufacturer of fuel systems.