(1980 to 2003) Components include a timing rotor (timing cup), sensor plate or inductive pickup, ignition control module, ignition coil and spark plugs. For electronic advance, the inductive pickup generates TDC pulses that are sent to the solid state Ignition Control Module (ICM). The ICM computes ignition timing advance and coil dwell. In 1983, a Vacuum-Operated Electric Switch (VOES) was added to switch between 2 different spark advance curves built into the ICM. ¹⁾

This uses a Dual-Fire Spark system, using only one coil trigger wire to produce a spark on both plugs at the same time. (See coil information)

The spark advance start point can be altered by physically moving the sensor plate in the “nosecone”.

The 1998-2003 Sport model was an exception. It pioneered the Single-fire Spark system and the Manifold Air Pressure sensor (MAP) on the Sportster line. Both were utilized across the line on the 2004-later models.

(2004-2006) The Ignition Control Module (ICM) became more capable and included a digital communications link (SDB) between itself and the Turn Signal Module and the Speedometer. This new Serial Data Bus (SDB), using an accessible data port on the side of the bike, also allowed the ICM to be dealer programmed for either 883 engines or 1200 engines.

The newly added Crankshaft Position Sensor (CKP) replaced the camshaft pickup as a more advanced means of sensing the engine revolutions and the new Manifold Air Pressure sensor (MAP) replaced the VOES as a more advanced means of sensing engine loads. The ignition system gives a spark near top dead center for starting. Then, at running RPM and loads above this, the system gives a spark advance that varies between 0 and 40.

From this point forward, the Sportsters used a Single-fire Spark system, using two individual coil trigger wires to produce a spark on individual spark plugs, one at a time. (see coil information)

(2007 - 2013) With the implementation of Electronic Fuel Injection, the Electronic Control Module (ECM) is the heart of the ignition system. It obtains inputs and controls outputs as listed below. This expanded capability for the ECM allows it to be programmed in minute detail to account for changing conditions in the operating engine.

The ECM obtains input information from:

• Manifold Air Pressure Sensor (MAP)
• Crank Position Sensor (CKP)
• Engine Temperature Sensor (ET)
• Intake Air Temperature Sensor (IAT)
• Oxygen Sensors in Exhaust (two) - (O2)
• Throttle Position Sensor (TPS)
• Vehicle Speed Sensor (VSS)

The ECM controls the following outputs:

• Serial Data Bus (digital) for Turn Signal Module & Speedometer
• System Power Control thru System Relay
• Idle Air Control (IAC)
• Fuel Injectors in Heads (two)
• Coil Firing Sequence - Single-Fire using Encapsulated dual-coils

(2014-on) To further expand the computerization of the Sportster, the ECM was equipped with a Controller Area Network Bus (CANBUS) and the Body Control Module (BCM) was added. In general terms, the CANBUS replaced the digital communications between the smart controllers (in place of the Serial Data Bus) and allowed computerization of the handlebar controls, while the BCM replaced the Turn Signal Module and handled power distribution throughout the bike, including to the lights and other components. It looks like 2015 also eliminated all relays.

ECM - Electronic Control Module
The ECM is mounted behind the rear cylinder. It computes the spark advance for proper ignition timing and fuel control based on sensor inputs (from ET, CKP, TMAP, TGS, HO2S and VSS sensors) and controls the low-voltage circuits for the ignition coils and injectors.

The ECM contains all of the components used in the ignition system. The dwell time for the ignition coil is also calculated in the microprocessor and is dependent upon battery voltage. The programmed dwell is an added feature to give adequate spark at all speeds. (The ECM has added protection against transient voltages, continuous reverse voltage protection and damage due to jump starts.) The ECM is fully enclosed to protect it from vibration, dust, water or oil. This unit is a nonrepairable item. If it fails, it must be replaced. When the ECM is replaced, see the service manual.

32-2 Flywheel
The left flywheel has 32 teeth positions - 30 teeth are evenly spaced around its circumference with two consecutive teeth missing (sync gap). In this configuration, the ECM determines engine position, engine phase and engine speed from the CKP sensor input. Phase (TDC compression) is determined by the ECM during startup and, when necessary, while running. No engine ignition events can occur until the ECM determines the relationship of piston position to crankshaft position. The following paragraphs (see note below) describe synchronization and phasing by the ECM to provide smooth operation of the engine at all speeds.

Crank Position Signal Synchronization
In the 32-2 crank configuration, crankshaft position is determined by the ECM finding the empty two-tooth sync gap in the CKP sensor signal. This is usually accomplished the first time the sync gap is encountered. The ECM monitors the CKP signal status every engine revolution. If the ECM determines synchronization is lost, it immediately terminates ignition events and synchronizes on the next occurrence of the sync gap.

Engine Phase
Phasing is accomplished by the ECM identifying a widening in the CKP signal caused by the deceleration of the crankshaft, as a piston approaches TDC on its compression stroke. Since the rear cylinder approaches TDC earlier than the front cylinder, engine phase can be readily discriminated. Phasing is normally accomplished on the first TDC cycle after engine synchronization. Once phased, the ECM can begin normal ignition events. If the ECM experiences a system reset or loss of synchronization while the engine is running it also loses phase.

When phase is lost one of the following occurs:

• If an engine-not-running (Crank Mode) rpm is detected, the ECM executes the normal start-up phasing process.
• If Engine Run Mode is detected, the ECM executes a running re-phase sequence.

The front cylinder is fired every engine revolution. The ECM monitors the power stroke after the fire event to determine if sufficient acceleration occurred to indicate the ECM fired on the compression stroke. When two valid power strokes are detected, the ECM locks phase and resumes normal ignition events.

Engine Run Mode
Many functions of the EFI system require an engine run mode determination. Engine run is determined by the level of engine rpm. Generally, the engine is considered to be running when engine rpm exceeds a minimum of 750 rpm.

(Note: Quoted from “2013 Sportster Models Electrical Diagnostic Manual”, page 6-3)

• Aftermarket Ignition Swap: http://xlforum.net/vbportal/forums/showthread.php?t=1382357 ²⁾

(1986-2003 Evo)
The coil is a dual encapsulated unit with two coils in one housing. These coils are interconnected serially to produce a Dual-fire Spark system - The internal front and rear coils both fire at the same time which produces a wasted-spark on the cylinder that is not under compression. This coil has one trigger signal from the ICM for both coils. The Primary windings of the coil are typically measured at 3-ohms.

(2004-later Evo)
The coil is a dual encapsulated unit with two coils in one housing. It uses a Single-fire Spark system - The internal front and rear coils each fire their spark plug independently (one cylinder at a time - no wasted spark) when that cylinder is under compression. This coil has a front & a rear trigger signal from the ICM.

(1998-2003 Evo Sport)
These Sport models use a quad encapsulated unit with two dual-coils in one housing. Using dual spark plugs in their heads, these models utilize a Single-fire Spark system - The internal front and rear coils are independent, only firing when their cylinder is under compression. Each (front or rear) dual-coil fires a dual-plug-set. This coil has a front & a rear trigger signal from the ICM.

*= The resistance specification in the manual is for one coil only (measured from PinB(04-later) to either tower) - the tower-to-tower measurement would, therefore, be twice that amount as it represents both coils in series - which is the spec shown above.
From the manual, 04-06 model is listed as 5500-7500ohms ³⁾
From the manual, 07-up model is listed as 1500-2400ohms ^{4) 5) 6)}

=== Does Ignition Coil Polarity Matter? ===

The short answer is NO. In fact, the way the dual-fire coils are wound, one plug fires tip to base and the other fires base to tip. Most modern coils provide levels of high-voltage (typically, 30,000 volts or more) that exceed any normally required level for standard spark plug gaps. On connectorized coils, be sure any modified wiring matches the connections and polarity specified in the schematics.

See this excellent __XLForum Thread__, especially Post#20 by Fe Head.

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Coil part numbers have changed several times over the years. The primary resistance values below are typical, but check your FSM for the exact values for your year and model. For aftermarket products, check the primary resistance value with the manufacturer’s data.

How-it-works by Steelworker: An ignition coil is a pulse-type transformer, consisting of a low voltage primary winding (the input) and a high voltage secondary (output) winding, wrapped around a laminated iron core. The primary circuit is completed by the points or electronic ignition module closing the primary circuit to ground. The flow of current in the primary windings induces a strong magnetic field in the laminated iron core. When the primary circuit is broken (by the ground being removed), the strong magnetic field in the core collapses suddenly, which induces a high voltage electrical discharge out of the secondary circuit, thereby, producing a spark strong enough to bridge the electrode gap of each spark plug.

Testing - In General
To test the coil, you will need a multimeter (or DVM) with a low-resistance scale, preferably a scale of 200 ohms or less. Most coils have a primary resistance below 10 ohms and a secondary resistance in the 1,000's of ohms. When testing the primary resistance, you will connect the meter leads to only the primary connectors. When testing the secondary resistance, you will connect the meter leads, typically, to the coil output towers for the spark plug wires.

If the resistance measurements are lower than specified, that winding has partially shorted, bypassing part of the coil. If the resistance is higher, then corrosion or failing internal connections may be adding to the resistance. If the resistance is infinite, the winding is an open circuit. Failing coils cannot be repaired and need to be replaced with compatible products.

Sometimes coil failure is heat related. In that case, simply idling the bike and heating the coil with a hair dryer may cause the coil malfunction to occur and the spark to stop or become intermittent or erratic.

Two different type coils:
There are two basic ignition systems and HD used different coils for each. The dual-fire ignition systems (thru 2003) use a double-coil built into one housing and both coils are always fired together - One output for the front cylinder and one output for the rear. Both coil outputs fire together when the front cylinder needs a spark and both coil outputs fire together when the rear cylinder needs a spark.

Later (2004+), the single-fire ignition system became standard. It uses a double-coil also built into one housing, BUT, each coil fires separately. One coil is charged and fired when the front cylinder requires a spark and the other coil is charged and fired when the rear cylinder requires a spark. Each coil is SINGLY fired when it's cylinder needs a spark.

⁷⁾

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Dual-Fire Coil Testing (1986-2003)(Except Sport Model - See Below)
The Dual-Fire Coil has only two primary screw terminals (sometimes labeled, + & -) with dual output towers to the spark plugs. 1986-2003 Evos use a coil rated, nominally, at 3.0 ohms (HD P/N 31614-83A). It has primary terminal studs and the primary wires are nutted onto the coil.

The primary resistance is measured across the two input terminals at 2.5 to 3.1 ohms. Secondary (high voltage) winding resistance is tested from coil tower to coil tower. While the actual specs do vary, typically, the range is 10,000 to 12,500 ohms. Check the FSM for the exact primary and secondary coil resistance for your model year.

(Note that Ironheads with points typically use a dual-fire coil with a nominal primary resistance of 5.0 ohms.)

2-Dual-Fire (Quad) Coil Testing (Sportster Sport 1998-2003)
The Sport model is unique - It has two spark plugs in each head. This means the coil must fire four separate spark plugs. To do this, the Sport model coil (HD P/N 31646-99) has four internal coils in one housing. They are wired so both front cylinder spark plugs are fired together by two of the coils and then the rear cylinder set of plugs are fired by the other set of coils.

The coil output towers exit at right angles to the Sportster frame. The Front (Left & Right) towers fire the two plugs in the front head. The Rear (Left & Right) towers fire the two plugs in the rear head. The coil primary windings are connected using a 3-pin connector located on the coil just below the upper frame.

The coil has three connectorized primary terminals referenced as pin A(Front), B(V+) and C(Rear). Pin A & C connect the appropriate firing signals and primary terminal pin B(V+) is common to all internal coils. Primary resistance from pin B(V+) to pin A(Front) is 0.4 to 0.6 ohms and likewise the same for pin B(V+) to pin C(Rear). The secondary resistance measurement is taken between both front coil towers (L&R) and then again between both rear coil towers (L&R). The measurement for each is 11,700 to 12,700 ohms.

Single-Fire Coil Testing
The Single-Fire Coil has a separate firing signal input for the Front & Rear plugs.

2004-2006 models - The coil (HD P/N 31655-99) has three connectorized primary terminals referenced as pin A(Rear), B(V+) and C(Front). These same pins are also referenced as 1, 2 & 3, respectively. Pin A & C connect the appropriate firing signals and primary terminal pin B(V+) is common to both internal coils. Primary resistance from pin B(V+) to pin A(Rear) is 0.5 to 0.7 ohms and likewise the same for pin B(V+) to pin C(Front).

You can test the secondary resistance of each individual coil by placing one meter lead on the B(V+) input terminal and then placing the other meter lead on one of the output towers - Taking the reading this way should produce a resistance reading within the range specified in the manual, 5500-7500 ohms. If you test the secondary resistance between both towers (one lead in each tower) you should obtain a reading equal to the sum of the two previous readings - or 2x the spec - Here, that would be a reading between 11,000 & 15,000 ohms.

2007-2013 models - With the introduction of EFI, the single-fire coil (HD P/N 31656-07) has four (4) connector pins in the connectorized primary connector. Looking into the connector on the coil (when the towers are pointing down), the pins (left-to-right) are defined as A(Power), B(Power), C(Rear) & D(Front). Both PinA & PinB are supplied power together by the connecting cable. The C(Rear) & D(Front) pins are the trigger signals, which are grounded by the Engine Control Module (ECM) to charge the coil and released from ground to fire the coil.

Measuring primary coil resistance from pin A to pin D should read 0.3 to 0.7 ohm. Likewise, from pin A to pin C should measure 0.3 to 0.7 ohm.

Maybe» Although PinB is supplied power, it is believed that PinB is connected between the two secondary coils, allowing for the future implementation of ION Sense, the ability to detect combustion when the spark plug fires.

You can test the secondary resistance of each individual coil by placing one meter lead on the PinB terminal and then placing the other meter lead on one of the output towers - Taking the reading this way should produce a resistance reading within the range specified in the manual, 1500-2400 ohms. If you test the secondary resistance between both towers (one lead in each tower) you should obtain a reading equal to the sum of the two previous readings - or 2x the spec - Here, that would be a reading between 3,000 & 4,800 ohms.

2014-later models - The operation for these years is the same as above, except for PinB. In 2014, with the implementation of the CANbus, PinB began to be used for ION Sense, with a separate wire back to the ECM (Pin9). ION Sense allows the ECM to sense combustion when the spark plug fires.

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1986-1990 The Ignition Control Module (ICM) is located rearward of the battery behind the triangular cover. The ICM is directly wired to the main harness or it's related components. THERE IS NO CONNECTOR TO USE FOR TESTING. You will need to test at the coil.

On the coil, the BLUE Wire is the trigger wire from the Ignition Control Module & the PINK Wire goes to the Tachometer. The WHITE Wire(s) are power from the Run/Stop Switch.

Remove the BLUE & PINK Wires from the coil - There should now be no wires on that electrical post of the coil. Leave the WHITE wire(s) connected to the other electrical post.

Connect an appropriate length wire to a solid ground point on the frame, long enough to reach the coil. Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark. You can always use an extra hand clamp.

Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

Briefly ground the coil by touching your ground wire to the coil electrical post where the BLUE & PINK Wires were previously connected. This will charge the coil and it should fire a spark on both plugs when you remove the wire from the coil.

This will test the coil, spark plug wires & spark plugs to verify a spark is able to be produced. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

1991-1993 The Ignition Control Module (ICM) is located rearward of the battery behind the triangular cover. It connects to the main harness at Connector 10A/B - a seven-pin connector located behind the battery near the circuit breakers.

Remove connector 10A from 10B - On the pin side (10A), which goes to the main harness, Pin#4 (BLACK Wire) is connected to the main ground while Pin#1 (PINK Wire) provides the trigger for the coil.

Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark. Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

NOTE » VERIFY YOUR CONNECTIONS BY COLOR - TAKE CARE NOT TO SHORT ANY OTHER PINS

Use a short piece of wire to briefly short Pin#4 (BLACK) to Pin#1 (PINK) on Cable Connector 10A - By briefly shorting these pins, you will charge the coil and it should fire a spark on both plugs when you remove the wire from those pins.

This not only tests the coils, but all the wiring from the 10A/B connector to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

1994-1997 The Ignition Control Module (ICM) is located rearward of the battery behind the triangular cover. It connects to the main harness at Connector 10A/B - an eight-pin connector located behind the battery near the circuit breakers.

Remove connector 10A from 10B - On the pin side (10A), which goes to the main harness, Pin#7 (BLACK Wire) is connected to the main ground while Pin#4 (PINK Wire) provides the trigger for the coil.

Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark. Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

NOTE » VERIFY YOUR CONNECTIONS BY COLOR - TAKE CARE NOT TO SHORT ANY OTHER PINS

Use a short piece of wire to briefly short Pin#7 (BLACK) to Pin#4 (PINK) on Cable Connector 10A - By briefly shorting these pins, you will charge the coil and it should fire a spark on both plugs when you remove the wire from those pins.

This not only tests the coils, but all the wiring from the 10A/B connector to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

1998-2003 ALL Except Sport Model
The Ignition Control Module (ICM) is located behind the small timing cover on the Cam Cover. It connects to the main harness at Connector 10A/B - a six-pin connector located under the engine.

Remove connector 10A from 10B - On the socket side (10B), which goes to the main harness, Pin#6 (BLACK Wire) is connected to the main ground while Pin#4 (PINK Wire) provides the trigger for the coil. (Some early versions may have the PINK Wire on Pin#5)

Now take a short piece of wire (paper clip?) and ground one end by inserting it into Pin#6. Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark.

Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

Now, very briefly, touch the ground wire to socket Pin#4 of Cable Connector 10B - By briefly touching that pin, you will charge the coil and it should fire a spark on both plugs when you remove the wire from Pin#4.

This not only tests the coils, but all the wiring from the 10A/B connector to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

1998-2003 (Sport Model only)
The Ignition Control Module (ICM) is located under the seat. It connects to the main harness with two 12-pin connectors - one Gray Connector (11A/B) and one Black Connector (10A/B) - We want to disconnect both, but will only be working with the 10B socket connector.

Remove connectors 11B and 10B from the ICM - On the socket side of 10B (the Black connector), which goes to the main harness, Pin#2 (BLACK Wire) is connected to the main ground while Pin#6 (BLUE/Orange Wire - Front) and Pin#7 (YELLOW/Blue Wire - Rear) provide the triggers for the dual-coil.

Now take a short piece of wire (paper clip?) and ground one end by inserting it into Pin#2. Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark.

Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

Now, very briefly, touch the ground wire to Pin#6 of Cable Connector 10B (the connector on the cable, not on the ICM itself) - By briefly touching that pin, you will charge the coil for the FRONT plugs and it should fire the front cylinder spark plugs when you remove the wire from Pin#6.

Now briefly touch the ground wire to Pin#7 of Cable Connector 10B - This will energize the coil for the REAR plugs and when removed that coil should fire the rear cylinder spark plugs.

This not only tests the coils, but all the wiring from ICM to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

2004-2006 ⁸⁾
Find the Ignition Control Module (ICM) under the seat - Remove the connector from the ICM (12 pin connector known as 10A/B). On that connector, Pin#5 (BLACK Wire) is connected to the main ground while Pin#6 (BLUE/Orange Wire - Front) and Pin#7 (YELLOW/Blue Wire - Rear) provide the triggers for the dual-coil.

Now take a short piece of wire (paper clip?) and ground one end by inserting it into Pin#5. Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark.

Turn the keyswitch fully on - Flip the Run/Stop switch to RUN.

Now, very briefly, touch the ground wire to Pin#6 of Cable Connector 10B (the connector on the cable, not on the ICM itself) - By briefly touching that pin, you will charge the coil for the FRONT sparkplug and it should fire a spark when you remove the wire from Pin#6.

Now briefly touch the ground wire to Pin#7 of Cable Connector 10B - This will energize the coil for the REAR plug and when removed that coil should fire the rear spark plug.

This not only tests the coils, but all the wiring from ICM to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

2007-2013 With the implementation of the Eletronic Fuel Injection Ignition System, there is now a System Relay. The Engine Control Module (ECM) is located under the seat.

Remove the connector from the ECM (36 pin connector known as 78A/B). On the socket connector (78B), Pin#10 (BLACK Wire) is connected to the main ground while Pin#29 (BLUE/Orange Wire - Front) and Pin#11 (YELLOW/Blue Wire - Rear) provide the triggers for the dual-coil. Pin#2 provides the grounding activation for the System Relay.

Take a short piece of wire (paper clip?) and ground one end by inserting it into Pin#10. Then, place the other end into Pin#2 to create the missing activation signal for the System Relay. Remove your spark plugs and ground them to a solid ground point (like the fins) where you can observe the elements for a spark.

Place another short piece of wire (paper clip?) into Pin#11 and short it to Pin#10. Turn the Run/Stop switch to OFF/STOP - Turn the keyswitch fully on. Now, briefly, flip the Run/Stop switch to RUN and then back to OFF/STOP. By briefly activating the RUN switch, you will charge the coil for the REAR cylinder and it should fire the rear spark plug when you switch back to OFF/STOP. Turn the keyswith to OFF.

Remove the wire from Pin#11 and place it into Pin#29 and short it to Pin#10. Turn the Run/Stop switch to OFF/STOP - Turn the keyswitch fully on. Now, briefly, flip the Run/Stop switch to RUN and then back to OFF/STOP. By briefly activating the RUN switch, you will charge the coil for the FRONT cylinder and it should fire the front spark plug when you switch back to OFF/STOP. Turn the keyswith to OFF.

This not only tests the coils, but all the wiring from ICM to the Spark Plugs. Power down and put everything back where it belongs.

If this test fails to produce a spark at each spark plug, and the spark plug wires and spark plugs are functional, then the coil itself is suspect. A (temporary) replacement coil should be utilized and the test performed again.

2014-later Because the ECM/BCM is so fully integrated with all the operating components, it controls power to the coil. It is no longer a simple matter to test from the ECM to the coil.

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This information applies to 1986-1997 All Models & 1998-2003 'S' Models
These models use a Cam Sensor Plate that is separate from the Ignition Control Module.

This information does not apply to the non-'S' models of 1998-2003 which use an integrated Ignition Control Module on the Cam Sensor Plate in the nosecone. It also does not apply to 2004-later models which use a Crankshaft Position Sensor (CKP) instead of a Cam Sensor.

The Cam Sensor connects thru the main wire harness to the Ignition Control Module. It uses a 3-pin connector, known as 14A/B. It is located under the engine (left side near the kick stand). The 14A (plug) comes from the Cam Sensor Unit - the 14B (socket) is on the main harness and goes to the ICM.

On Connector 14B (3-pins), the wires function as follows:

• Pin(A) Red/White - 12v Power from ICM to Cam Sensor ⁹⁾
• Pin(B) Green/White - Rotor Signal from Cam Sensor to ICM
• Pin(C) Black/White - Ground from ICM to Cam Sensor

(Note: the 1998-2003 Sport models use the same Cam Sensor & Connector as the 1994-1997 models)

Testing the ability of the ICM to sense the Cam Rotor & fire the Coil

• With the rest of the wiring in tact, disconnect the Connector 14A/B
• Turn the Keyswitch to ON & place the RUN/STOP switch in the RUN position
• Using harness Connector 14B (which goes to the ICM), briefly short Pin(B) to Pin(C) using a paper clip in the sockets
• Note: The first four signals are ignored so do this 6-10 times
• After the first four tims, when the short is broken, the ICM should fire the coil
• (CAUTION - Never short (A) to either other pin or to ground)

If this test fails to produce a spark at each spark plug, and the spark plugs, spark plug wires and coil are functional, then the Ignition Control Module itself is suspect. A (temporary) replacement ICM should be utilized and the test performed again.

If this test succeeds, yet no spark is produced when cranking the engine with the Cam Sensor connected, then the Cam Sensor is suspect and may need replacing. (Note: The Cam Sensors fail very rarely. Double check your testing.)

• The VOES was first installed on Sportsters in 1983 (and used on most models thru 2013). The unit senses intake manifold vacuum at the carburetor and requests that the Ignition Control Module switches between one of two different spark advance curves. The switch is closed at high vacuum operation, utilizing a more advanced spark curve and it is open at low vacuum operation, utilizing a less advanced (retarded) spark curve to minimize engine knock and still maintain performance. The VOES is installed above the intake manifold. ¹⁰⁾

• VOES: Its Operation & Adjustment. (Article by IXL2Relax of the XLFORUM)¹¹⁾
  • There are many discussions on the XLForum and elsewhere regarding the VOES unit. While there are many helpful posts among those discussions, there is still much confusion due to posts that are inaccurate. I hope to clarify the VOES operation with this post and a reference diagram.
  • The VOES unit was used on the Sportster from about 1983 (Ironhead) to 2003 (Evos). But, note that the 1998 to 2003 Sport models did not have a VOES but rather pioneered the use of a MAP sensor like that used on 2004 and later model Sportsters. Those models have Engine Control Modules which can micro-manage the ignition advance based on multiple conditions.

Here's what the VOES looks like with a quick reference chart of it's operation:

• .
  • What it does and how.
    • The VOES works in conjuction with the ignition module to control ignition timing. The ignition module has two timing curves - one is for idling or cruising and the other is for WOT and/or for powering up for high loads (like steep hills). The VOES switches the ignition module between these two pre-programmed advance curves based on manifold vacuum.
    • The VOES has two connections and one adjusting screw. The VOES is connected to the carb (manifold side) through a vacuum hose and monitors the manifold vacuum level. It is also connected to the ignition module. It has two black wires from the internal switch. From the inline connector, there is a (purple or purple/white) single wire sent to the ignition module and a second wire sent to ground. The VOES switching point is set by a concealed screw. This causes the ignition module to switch between the two advance curves based on a set point level of manifold vacuum.
    • The adjusting screw is inside a sealed opening on the VOES. You must dig out the silicone sealing compound in order to make any adjustments. Remember - When testing your adjustments, you must also seal that opening with your thumb (or other air-tight sealing compound or tape) in order to prevent air leakage through the screw adjuster.
    • The only function of the VOES is to switch between the two advance curves that are programed into the ignition module. Different ignition modules have different curves. Those curves have anywhere from 5 to 18 degrees difference in the advance settings between them. But that's another discussion.
    • The manifold vacuum directly controls the VOES, but the throttle position (and/or it's aggressive changes) indirectly alters the VOES (thru changes in the manifold vacuum) by altering the carburetor throttle plate.
    • When the engine is running at idle, when lightly accelerating or when using a steady cruise throttle, manifold vacuum is high (the throttle plate is mostly closed) and the VOES switch is ON, causing the ignition module to use the MORE ADVANCED CURVE.
    • When the engine is not running or when the throttle is quickly opened to accelerate or to satisfy a heavy load (steep hill, extra weight, etc.), the manifold vacuum drops and the VOES switch goes OFF, causing the ignition module to use the RETARDED (OR LESS ADVANCED) CURVE. If you let off the throttle (when you reach your speed or top the hill), the manifold vacuum rises again. The VOES senses this and will again switch ON, causing the ignition module to return to the MORE ADVANCED CURVE as the load on the engine becomes lighter.
    • Running without a VOES causes the ignition to run on ONLY the less-advanced power curve. The ignition module cannot switch curves. Unless you have a highly modified engine, this will hamper smooth engine operation on light acceleration and reduce fuel savings during cruising.
    • Also note, if the VOES switching point is set too low, it will remain on the more advanced curve too long under mid-load acceleration and pinging will occur. This is the reason that engines with upgraded performance should have their VOES switch point increased (switch at a higher vacuum level) to better match the capabilities of the engine.
  • Testing the VOES Switch Point
    • To test your VOES unit (or adjust it to a specific switching point), you will need a vacuum pump (with gauge) to create the desired vacuum level and an ohm meter to test whether the VOES has switched on (causing a short between it's wires).
    • To work on the VOES, remove the vacuum hose from the vacuum line tee where it branches to the vacuum-operated petcock. If you don't have a vacuum-operated petcock, and have no tee, you need to remove the vacuum hose from the carb. Then remove the VOES from it's mount under the fuel tank and disconnect the wires.
    • Connect your vacuum pump to the hose and connect your meter (set on ohms) to both wires. As you slowly pump up the vacuum, there will come a point where the meter will switch from infinity to zero ohms. This is the switch point. Write down the indicated vacuum (inches of mercury). Release the vacuum and do the test again, just to be sure you get a consistant reading.
    • If the reading is right (according to the manual or chart above) for your bike, you can leave it as it is. If your bike is stock or only upgraded to Stage 1 level, you probably do not need to alter the factory VOES setting. But if you've gone farther with your mods, you might have one of those engine builds where the combination of ignition curves, cams, heads, etc., leaves you with some pinging near the VOES switch point. If you want to make your VOES switch at a different point, read on.
  • Adjusting the VOES Switch Point
    • Dig out the original sealing compound which fills the opening where the adjusting screw is located. Do this carefully so as not to damage the internal screw or diaphragm or the VOES housing. Remember - When testing your adjustments, you must also seal that opening with your thumb (or other air-tight sealing compound or tape) in order to prevent air leakage through the screw adjuster which will skew your readings.
    • To adjust the VOES to switch at a higher vacuum, turn the adjuster screw 1/4 turn clockwise. Now repeat the test from above to see where (in inches of mercury) the new switch point occurs. If you want it to switch at a lower vacuum level, turn the adjuster screw 1/4 turn counter-clockwise. Keep adjusting the screw (carefully) to raise or lower the switch point. You should not go more than 1 or 2 full turns from the initial setting. If you turn the screw too far clockwise, you'll damage the internal diaphragm and need to replace the unit.
    • When you are done making adjustments, you'll need to plug up that hole. But do this very carefully - Be sure you DON'T GET ANY SILICONE DOWN NEAR THE SCREW. Use only enough to plug the end of the opening and then set it aside to fully cure (probably 24 hours) before reinstalling on your bike.
  • Variety of VOES
    • From the book '101 HD Evo Performance Projects by Kip Woodring & Kenna Love', HD installed VOES on different models with their adjustment set for different switching points. These vacuum settings are measured in inches of mercury. The VOES are color-coded at the sealed end to indicate what setting was used on a particular unit. (I have seen very few with colors other than the natural greyish white - so perhaps HD did not keep up this practice)
    • No Color - - - 7.0 in. Mercury – Early Evo FLT (1984)
    • RED Color- - - 5.5 in. Mercury – Late Evo FLT
    • WHITE Color - 4.0 in. Mercury – Evo FXR & XL
    • BLUE Color - - 4.0 in. Mercury – Evo Softail
    • All of these VOES should be adjustable to other settings. As far as I know, there is no difference in the various VOES units themselves other than their predefined factory settings.
    • The 2003 Sportster Service Manual says the correct Sportster VOES has a Blue paint mark at the vacuum hose fitting ¹²⁾

* READER BEWARE!!! …NOT EVERYTHING YOU READ ONLINE IS VALID INFORMATION…

• There's a lot of MIS-information about the VOES & its operation!
• There are many threads with references to the VOES and how it works, or how it should be adjusted, or what effect it will have. I've only posted above some of the information that is valid. But there is so much confusion surrounding the VOES that you must read all statements carefully to keep from being misled.
• There is a Sticky Thread in the 'Engine Conversion' section titled 'VOES ADJUSTMENT' - Be careful of the information presented there regarding the VOES. “This is the most confusing conglomeration of instructions I have ever read. There is some bad info, some completely wrong info, and some very dangerous info.” (A comment from Post# 113)
• That thread has some information about connecting an LED light to the VOES-to-Ignition wire to see the VOES switching modes while riding. If you try this, just be careful to read the information thoroughly and understand what you're doing before proceeding. This is the link to that thread: http://xlforum.net/vbportal/forums/showthread.php?t=57534

• Additional References:
  • For the sake of not repeating what can be looked up directly, the following links have VOES discussions (as well as other info).
    • http://xlforum.net/vbportal/forums/showthread.php?t=5945
    • http://xlforum.net/vbportal/forums/showthread.php?t=594019 - Thread not all VOES related
      
    • These posts from the above thread are most applicable:
    • . . http://xlforum.net/vbportal/forums/showpost.php?p=2210315&postcount=173
    • . . http://xlforum.net/vbportal/forums/showpost.php?p=2210326&postcount=174
    • . . http://xlforum.net/vbportal/forums/showpost.php?p=2210400&postcount=180
    • This post has some great pictures of the inside of the VOES:
    • . . http://xlforum.net/vbportal/forums/showpost.php?p=2210349&postcount=175
    • http://www.mklsportster.com/xlvoes.htm
    • http://www.wildwestcycle.com/f_voes.html

¹³⁾

• Ignition timing is when the spark takes place - specifically as the piston is traveling UP on the COMPRESSION stroke (compressing the gasses so that you get the most out of the explosion/ignition). ¹⁴⁾
• Top Dead Center is when the piston is at the VERY top of its travel - and is usually used to mean on TDC of the COMPRESSION stroke (with the valves closed and the mixture compressed), though the piston will also be a TDC of the Exhaust stroke when the flywheel turns one complete rotation in either direction from TDC of compression. ¹⁵⁾
• Spark ADVANCE - is how soon, BEFORE the piston reaches top dead center (or how late - AFTER top dead center) that the spark plug fires to start burning the mixture. The faster the motor is turning, the sooner you need to start the ignition (more advanced it needs to be) so that power of the expanding gasses starts pushing on that piston as soon as it starts moving downward and pushes as long as will be beneficial. ¹⁶⁾
  • Ignite it too soon, and the gasses start pushing down as the piston is still coming up (spark knock, pinging etc). ¹⁷⁾
  • Ignite it too late, and you loose a lot of the power of the gases, since the piston will reach bottom before the gasses finish expanding. ¹⁸⁾

• The MAP sensor is the accrostic for Manifold Absolute Pressure. It is connected to the intake manifold on both EFI and Carbureted engines to monitor the changes in the vacuum (pressure) that are occuring as you ride, change speeds and vary the load via the throttle position. It is temperature compensated and uses a complex algorithm to help offset the pulsating wobble effect of the HD V twin's assymetrical firing setup. ¹⁹⁾
• It is a very major component of the final speed density calculation that ulimately determines the injector's pulse width required to sustain the best A/F ratio at any given time - for EFI setups. In Carburetor versions it assists in monitoring the degree of advance for the timing of the spark plugs.²⁰⁾
• There are several codes that it can throw out such as: ²¹⁾

• The P0107 indicated that the reading was either absent or fell below the minimum range for a some period of time. If not calibrated correctly or working properly the ECM will fix a canned value and use the other inputs to adjust the A/F ratio. It will in an EFI setup greatly affect your richness/leaness if it is skewed or not registering accurate readings.²²⁾
• More advanced systems also use a second sensor to adjust / monitor the Barometric Pressure and then use it as an offset depending on your elevation and the local atmospheric conditions. ²³⁾

TESTING the MAP SENSOR

• This requires a digital multi-meter set to the 0 - 20 volt dc setting. ²⁴⁾
• Typically most MAP sensors are simply a set of resistive strain guages mounted on a siutable substrate and forming a bridge circuit. ²⁵⁾
• With the ignition switch turned to ON, test each of the three leads as follows: ²⁶⁾

1. Probe each lead an verify which is the +5 volt input signal.
2. Remove the hose from intake manifold and if needed add an extension to it so you can easily apply a vacuum with your mouth.
3. Draw as much vacuum as you can and seal it with your tongue while probing the other two leads to see which is the signal out lead at 3.5 to 4.5 volts.
4. Then release the vacuum slowly and see the voltage drop as you do confirming the lead signal functions.

• This will confirm the functionality of the MAP sensor.
• This signal is the one that the ECM uses to assess the state of load on the engine relative to the Throttle Position Sensor and the tachometer reading. ²⁷⁾
• The HD MAP sensor has a thermister as well to register the intake temperature. ²⁸⁾