Test #2: Ignition Harnesses (leads) + Spark Plugs.

steps for spark plug INSTALLATION

-All polarity is same in a horizontally opposed engine -Reverse polarities (top to bottom, vice ver) and next firing order when re-installing spark plugs -anti seize starting on 2nd thread so it doesn't get on electrodes -new gasket / clean threads. NO GASKET ON SPARK PLUGS W/ THERMO COUPLE -proper torque on plug -terminal installed finger tight, then turn about 1/8 of a turn with a wrench.

steps for spark plug TESTING

-Bomb Tester, tests spark plug under pressure (200 psi approx) and places high voltage across electrodes to see if spark plug fires constantly. -After cleaning and testing, if the spark plugs are not immediately installed, threads should be protected by rust-inhibiting oil and placed in cartons. Also inhibit moisture.

all steps for spark plug GAPPING

-Massive Electrodes: move ground electrode so it remains parallel w/ center electrode (gap between .016" - .021"). -Use "go" "no go" round wire gauge, must not be between electrodes when ground electrode is moved in. Close the gap only, never widen the gap as this may damage the insulation -Fine wire, bend gorund electrodes toward the center electrode until gap between two is the same in diameter as wire gauge that's part of the tool.

List all the steps for spark plug REMOVAL

-Remove the terminal lead from the spark plug shielding using two wrenches. One to hold the spark plug in place, and the other on terminal -pull straight out of terminal cavity or else may damage the ceramic terminals (insulation) -special six point deep socket (usually magnetic) to loosen and remove the spark plug -Remove spark plugs and place them in numbered holes in a spark plug tray (top and bottom)

List all steps for spark plug INSPECTION

-Spark plugs should be replaced when the electrodes have worn to 1/2 their original dimension -Examine plugs for indicators of abnormal engine cylinder operation -DETONATION - severe / excessive electrode wear -Rich mixture - excessive amount of black fluffy carbon -Too much oil - Black, wet, oily deposits on the insulator tips (cause, worn or faulty piston rings or worn intake valves) -Lead fouled - firing end cavity filled with hard, brittle deposits (too much TEL in fuel) -Silicon contamination - shiny, dark brown deposit on the insulator tips.

all steps for spark plug CLEANING

-degrease and remove all contaminants -degreasing: electrode end placed in stoddard solvent, varsol, or naptha for 20 - 30 minutes. Drain for 2 minutes then blow completely dry w/ compressed air. (NO DEGREASER IN TERMINAL CAVITY) -Loosen lead deposits from firing end w/ a vibrator-type cleaner. then remove residue w/ a glass bead or aluminum oxide abrasive blast (NO SILICON). DON'T BLAST FOR OVER 3 - 5 SECONDS (TOO MUCH = ERODING ELECTRODES) -Terminal cavity cleaned w/ a cotton or felt swab saturated w/ acetone (or fine abrasive like Bon Ami) -Clean threads w/ a brush or fine-wire brush (don't brush the insulator

✪✪✪ pg. 229 not made yet

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Rich mixture in an engine cylinder is indicated by what on the firing end of a spark plug?

excessive amount of black fluffy carbon (too much fuel)

Ignition harness issues that prevent sparks

it's possible for high voltage to leak to ground through the ignition leads and prevent the spark plug from firing. Leakage can be determined by using an ignition harness tester. Connect one lead from the tester to the center conductor and the other to the outer shielding.

Ignition Harness

A set of ignition leads. Carries high voltage from the distributor to the spark plug. It must be shielded to prevent radio interference from electromagnetic radiation, which is carried to ground.

All-weather spark plug

A shielded spark plug designed for high-altitude operation. A resilient seal (grommet) prevents water from getting into the terminal cavity.

Oil leakage (too much oil) in an engine cylinder is indicated by what on the firing end of a spark plug?

Black, wet, oily deposits on the insulator tips. Caused by worn or faulty piston rings or worn intake valves. The oil is conductive at low temperatures and will prevent the plug from firing.

✪✪✪ Fouling

Build up of a contaminant between the center electrode and ground electrode which may form a low-resistance path of high voltage to leak to ground, which would prevent the plug from firing. ie. Lead (from AVGAS, helps prevent detonation) Carbon Ice Bridging

What is spark plug insulation material made from?

Ceramic material made of aluminum oxide

Spark Plug Leads (barrel)

Connection point between the spark plugs and IGNITION LEADS (harness) Standard 5/8-24 spark plug. All-weather (high-altitude) 3/4-20 spark plug.

Capacitance afterfiring

Continuation of the spark across the electrodes gap in a shielded spark plug after the fuel-air mixture in the cylinder is ignited. Serves no useful purpose and ERODES THE ELECTRODE, SHORTENS ITS LIFE. A resistor is built into most shielded spark plugs between the ignition lead and center electrode to negate this effect.

Lead fouling in an engine cylinder is indicated by what on the firing end of a spark plug?

Firing end cavity filled with hard, brittle deposits of lead (too much Tetra-ethyl lead in the fuel for the engine)

Hot spark plug

Has a long insulator tip which is slow to dissipate the heat (long path for heat to travel to get into the cylinder head). Used in conjunction with engines that operate with LOW CYLINDER TEMPERATURES.

Cold spark plug

Has a short insulator tip which rapidly dissipates the heat (quickly releases the heat into the cylinder head). Used in conjunction with engines that operate with HIGH CYLINDER temperatures to minimize accumulation of lead deposits.

Using a Long-reach spark plug in a cylinder requiring a short-reach plug.

If a long-reach spark plug is installed in an engine that requires a short-reach plug, the lower threads (of the spark plug) will be damaged (heat damage and carbon formation) and can damage the bushing or heli-coil when the plug is removed. This same type of damage may occur if the spark plug gasket is left off when installed into the cylinder.

Using a Short-reach spark plug in a cylinder requiring a long-reach plug.

If a short-reach spark plug is installed in an engine requiring a long-reach plug, or if two gaskets are used, the lower threads in the cylinder head will fill with carbon. The correct spark plug cannot be installed until the carbon is removed. If the spark plug doesn't properly seat, heat cannot be properly transferred form the spark plug into the cylinder head, and hot combustion gases may escape around the threads and damage the cylinder head.

Reach of a spark plug

Length of the threaded portion of the shell that screw into the CYLINDER HEAD. Two standard reaches for 18-mm spark plugs Long: 13/16" threads Short: 1/2" threads

Fine-wire spark plugs

Made from precious metals such as platinum and iridium. They help prevent fouling (and ice bridging) by allowing combustion gases containing lead to be scavenged from the spark plug before they solidify and form a low-resistance path of high voltage to leak to ground.

Two basic elements of spark plug servicing

Removing the contaminants form the firing end and restoring the electrode gap to the dimension specified by the spark plug manufacturer.

Purpose of a Spark Plug?

Sole function is to conduct high voltage to an insulated contact inside the combustion chamber (cylinder), and to provide a gap across which the current can flow to ground (center electrode <-> ground electrode)

Massive Electrodes

Spark plugs that have more than one massive ground electrode to provide a large amount of metal to wear before the gap becomes excessive. generally have two, three, or four nickel alloy ground electrodes arranged around the center electrode to form gaps for the spark to jump

Types and composition of (High-tension) Ignition leads

Stranded wire and Coiled conductor. Both high-tension leads have high-voltage insulation around the conductor and a braided wire shield around the insulation.

Why do spark plugs deteriorate?

The arc across the electrodes which occurs each time the spark jumps removes metal from one of the electrodes.

Spark Plug Size

The diameter of the shell threads that screw into the CYLINDER HEAD. 18-mm & 14-mm (almost obsolete). The reach (length of the threaded portion of the shell) of these spark plugs come in long-13/16" threads and short-1/2" threads

Shielded spark plugs purpose?

To ground electromagnetic radiation to prevent radio interference. consists of a central conductor, an insulator, and an outer conductive shielding. These components make an effective capacitor (bad for spark plugs)

When using an abrasive last on a spark plug, what are some common precautions?

To only use glass beads or aluminum oxide, and to not blast for over 3-5 seconds as it will cause excessive erosion of the electrodes.

✪✪✪ Troubleshooting multiple bad ignition leads

When an ignition harness check indicates several bad leads, it is possible that the problem is in the distributor block.

✪✪✪ Massive electrodes and erosion

When the center electrode is positive, the ground electrode is worn more than the center electrode. But, during the spark when the center is negative, the center electrode is the most severely eroded. For horizontally opposed engines with even numbers, polarity of the spark is the same each time the plug fires (will be either center or ground that is most severely eroded). To counter this, spark plugs are returned to a different cylinder each time after servicing.

Indicator on spark plug electrodes that it should be replaced.

When the electrodes have worn to 1/2 their original dimension

Electrode

a conductor through which electricity enters or leaves an object, substance, or region

✪✪✪ Spark Plug Electrodes

most important component that creates the spark. must meed the following requirements: -they must allow the spark to jump at the lowest possible voltage -the spark must be intense enough (have enough energy) to ignite the fuel-air mixture -the electrodes must have the maximum operating life without changing the size of the gap -There must be a minimum opposition to the flow of combustion gases around the center electrode. This allows the lead forming gases to be scavenged before they solidify into lead deposits.

Optimal Heat Range of spark plugs

optimal range is between 1,000 degrees F - 1300 degrees F. Deposits that form in this range are low in volume, low in electrical conductivity, and least likely to cause spark plug fouling. Lead bromide and carbon form on spark plug's insulator nose when temp is below 900 degrees F. Lead fouling from tetra-ethyl lead from fuel form mostly when temperatures are above 1300 degrees F.

Detonation in an engine cylinder is indicated by what on the firing end of a spark plug?

severe / excessive electrode wear

Resistor spark plug

shielded spark plug with a resistor between the ignition lead terminal and the center electrode to prevent Capacitance afterfiring

silicon contamination in an engine cylinder is indicated by what on the firing end of a spark plug?

shiny, dark brown deposit on the insulator tips.