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BATTERY AND STARTER TESTING

THE STORAGE BATTERY

The storage battery is designed to chemically accept an electrical charge and store it until needed. Batteries have a number of characteristics and weakness xxxx are usually overlooked until it is too late. This is especially true on xxxxxxx xxxxxx xxxxxxxx garden equipment in which the entire charging and starting circuits accessories. The location of the battery is not a primary design and is usually not located to the batteries best advantage.

Electrical power is stored chemically in ihe battery. The xxxxxx xxxxxxx the battery must be maintained. Do not add chemicals xxxx xxxxxxx xxxxxx they will only destroy the chemical balance.

xxxxxx xxxxxx xxxxxxx xxxxxxxxxd refill it with clean water or acid. As the battery xxxxxxal composition of the electrolyte solution changes. xxxxxxyte is determined by the state of change of the xxxxxx xxxxxxxtyte with new would upset the battery's xxxxxx xxxxxxxS of electrolyte loss. The loss is water. The battery to operate with a low xxxxxxxxx xxxxxxxx xxxxxx xxxxxxx

xxxxxxxx xxxxxxx xxxxxxxxxx only a limited area below the plates hemmed.

xxxxxxxx xxxxxxxx explosive gas xxxxxxxxx xxxxxxxx is being xxxxxx xxxxipment xxxxxxxxxxxxxine

BATTERY TESTS

Several tests may be performed to determine the condition of the battery. Any one test will not ensure a complete analysis. Making an assumption about a cause of a problem based on only one test would be like a doctor's performing brain surgery on you because you have a headache when perhaps an aspirin would cure Et. Make as many tests as possible to determine the battery condition,

SELF-DISCHARGE

A common problem is dirt and moisture buildup on top of the battery which creates a path for current flow or discharge across the top of the battery. Check for this by connecting the negative voltmeter lead to the battery by touching the positive voltmeter probe several places 0:1 the insulated portion of the battery top. Any voltage found here is a result of leakage of current.

Clean the battery top. Use a baking soda solution to help remove corrosion and acid deposits. Do not allow the baking soda solution to enter the battery. Always wear safety glasses and wash your hands frequently when you work with a battery. Wash off any liquid that splashes on your face or arms.

SPECIFIC GRAVITY TEST

As the battery is charged and discharged, both chemical solution and its specific gravity (weight) are changed. The charge of each cell can be measured with a battery hydrometer. Hydrometers are calibrated to read correctly at 80° or room temperature. If the test must be made at any other temperature, a hydrometer with a temperature correction scale must be used to get an accurate reading.

Draw enough water into the hydrometer to allow the bulb to flout freely and to record the reading accurately. Perform this test on each cell of the battery and compare the readings. A fully charged battery should read near 1.280 These readings indicate only the state of charge the battery currently has placid on it, A perfectly good battery will read low if the charging system is not keeping it charged or if considerable cranking or accessory load has just been placed on it.

One really important indication is that whatever the state of charge of the battery, all cells should read the same. The cells are connected in series and the charge and discharge of each cell are equal. Any variation between the readings obtained from the cells indicates bad cells and a weakened battery. If this battery is continued in use, it will place extra load on the charging circuit and will have reduced cranking power.

BATTERY CAPACITY TESTS

The battery must be able to maintain voltage during the cranking operation. Just taking a voltage reading from a battery not in use does not tell much. A nearly dead battery can show full voltage (12.6 volts D.C) when no load is connected. The true test of capacity is the abiluy to maintain voltage while under load.

A simple battery test can be made by connecting a voltmeter across the battery while the battery is still on the equipment. The no-load reading should be 12.6 volts. Observe the voltmeter and crank the engine. Crank until the voltmeter drops to a steady hold position.

Caution: Do not crank longer than 15 seconds! The voltmeter reading should be above 9.5 volts. If the engine cranked at a good normal speed and if the voltage remained above 9.5 volts, the battery is satisfactory. Failure to pass this test could be caused by excessive starter draw. Check the battery by using the carbon pile method.

CARBON PILE TEST

A carbon pile is a variable load device. Connect the carbon pile in series with an ammeter. The ammeter will indicate the amount of load being placed on the battery by the carbon pile. Connect a voltmeter across the battery to measure the battery voltage. Adjust the carbon pile to three times the ampere-hour rating of the battery for 15 seconds and observe the voltmeter reading. Do not leave the load on the battery for more than 15 seconds because the battery will be quickly discharged. If the battery reading does not drop below 9.5 volts, the battery will provide dependable performance. If the battery drops below 9.0 volts, it is either defective or is not fully charged. Retest with a hydrometer, and recharge the battery if necessary. If a fully charged battery does not pass the test, it is defective and must be replaced.

EQUIPMENT

The ammeter and carbon pile used foT this test must be able to handle three times the ampere-hour rating of the battery being tested. Battery /Starter testers with a D.C. voltmeter, suitable ammeter, and carbon pile are available.

TEST RESULTS

TEST	INDICATION	SOLUTION
Visual	Loose hold-down clamp. Corrosion on battery posts and clamps. Top of battery wet. Frayed cables. Cracked case. Electrolyte level low.	Tighten clamp or replace with new one if necessary. Clean with baking soda solution. Possible overcharge. Check charging circuit. Repair or replace. Repair or replace battery. Refill with clean water. Could be caused by overcharging. Check charging voltage.
Self-discharge	Readings found across top of battery.	Clean battery with baking soda solution.
Hydrometer	All cells show 1.280 specific gravity. All cells show 1.280 except one. All cells read low but equal.	Fully charge battery. Bad cell-battery. Will fail soon. Battery probably OK. Needs charging,
Cranking capacity test	Voltage remained above 9.5 volts during cranking -engine cranked normally. Voltage dropped below 9.0 volts.	Battery OK. Battery defective or not fully charged. Check battery charge with hydrometer, Recharge and re test.
	Battery recharged, but voltage still drops below 9.0 volts during cranking. Battery stays above 9,5 volts, but starter slow or not working at all.	Battery detective or starter circuit problem. Check battery with carbon pile. Check starter circuit.
Carton pile text	Battery voltage remains above 9.5 volts while ammeter reads three times battery ampere-hour rating. Battery voltage drops below 9.0 volts.	Battery OK. Battery defective if fully charged. Check with hydrometer and retest.

REWIND STARTERS

A number of rewind starter types are used on small gas engines. Regardless of the type, they are subject to the same wear and abuse. Basically, they consist of a pull rope, recoil spring, and an engaging mechanism. The variations occur in the engaging mechanism. These mechanisms should be basically understood so that wear and mechanical failures can be determined. Since repair usually consists of just replacing the worn parts, detailed repair instructions are not necessary.

DOG TYPE

The dog type engaging mechanism consists of a notched starter cup mounted solidly to the flywheel which turns with the flywheel at all times. Inside the starter cup is the starter dog which is turned by the starter rope. A brake spring mounted under the starter dog housing causes a slight drag on the dog assembly so that when the starter rope is pulled, the dogs extend, engaging the notched starter cup. The slight drag caused by the brake spring also causes the dogs to retract out of the way of the spinning starter cup when the spring rewinds the starter.

FRICTION SHOE TYPE

The friction shoe type utilizes cam action to engage the friction shoe against a smooth starter cup. As with the dog type, a brake spring creates a slight drag on the shoe unit holding the shoes from turning until the cam under the shoes moves, pushing the shoes out against the starter cup engaging the starter rope with the flywheel.

BALL TYPE

When the engine is stopped, the balls roll down the inclined ramp to the center pawl. When the rope is pulled, the center pawl catches one of the balls and locks it against the starter cup engaging the pawl with the starter cup. As soon as the engine starts, centrifugal force carries the bails out into the recesses and they continue to turn with the engine. The pawl remains stopped with the rewind rope. This type screws onto the crankshaft and requires a special tool (see Flywheel Removal) to remove.

The ears cast on the starter cup are easily broken off if a hammer is used to loosen the starter assembly. The entire assembly slides on over the extended crankshaft and is removed as an assembly. On older models the unit is held together by a large snap ring which is easily pried out.

Newer units are sealed. The sealed cover may be removed by using a small chisel to pry off the retainer cover. Do not use a screwdriver because it will be necessary to strike it with a hammer to remove the cover and most screwdrivers were not intended to be struck with a hammer and they may explode.

When replacing the ball type starter unit, be sure that it slips freely over the extended crankshaft end because the crankshaft must turn inside the starter pawl. Failure of the shaft to turn freely inside the pawl will cause the starter to "catch" occasionally making a loud scratching sound. Polish the shaft as needed to remove burrs and rust so that the assembly slides freely on the shaft.

IMPULSE WINOUP TYPE

The windup starter uses one of the clutches described previously, but it allows the spring to be wound up tight while the fly wheel is held locked in place by a locking pawl. A fold-up handle ratchets around the crankshaft gear while the spring is being wound up. Once the spring is securely wound, the lock is released allowing the spring to crank the engine.

On older types the lock pawl tended to wear a groove in the aluminum flywheel resulting in partial "releases" of the flywheel while trying to wind the spring. Remounting the lock mechanism so that it engages the flywheel at a different point is sometimes possible or the flywheel may be replaced.

The entire starter assembly and blower housing can easily and inexpensively be replaced with the conventional recoil starter. See the manufacturer's literature for spring rewinding instructions for their model starter.

VERTICAL PULL STARTER

The vertical pull starter utilizes a starter gear that engages a gear ring on the flywheel. The small starter gear is fitted on a threaded shaft. The first partial pull of the starter rope causes the starter gear to move down the threaded shaft to engage the flywheel ring gear. As the recoil spring rewinds the rope, the gear moves back down the threaded shaft disengaging it from the flywheel. When the engine starts, the flywheel spins the small starter gear in the direction thai quickly disengages it from the flywheel.

STARTER CLUTCH SERVICE

Starter clutch problems usually are the result of worn parts or are caused by rust or dirt freezing up the parts, It is not usually a good idea to put grease or oil on the starter clutch parts because it may prevent good engagement and will collect gum and dirt. If the parts are clean, free of rust, and properly aligned, the clutch should engage firmly.

Always inspect for wear and replace all badly worn parts. For example, replacing the notched starter cup without replacing worn, rounded starter dogs would soon cause the cup notches to wear out again. Replacement parts are usually inexpensive and ensure good operation. tf several parts are badly worn, consider replacing the entire starter unit.

ELECTRIC STARTER - BENDIX DRIVE

The electric starter is similiar to the D.C. generator in that it has a field wound on Held pole shoes and a turning armature that is connected to the circuit through the commutator and brushes. Generally, the armature winding is much heavier wire to allow greater current flow and thus develop the great torque needed to turn the engine.

Small gas engines do not pose the same problems as does the high-compression automotive engine. In additon to being much smaller, most small gas engines incorporate some type of compression release technique to provide for easy pull rope starting. Speed reduction and torque increase are achieved by the very small starter pinion gear meshed with the large flywheel ring gear. Reductions of up to 20-1 are achieved.

The starter is most commonly engaged to the flywheel by a Bendix type drive that utilizes a spring loaded pinion gear fitted to a threaded shaft. The sudden start of the starter motor causes the pinion gear to thread itself out on the shaft untO it hits the stop washer.

Then the pinion gear must turn with the starter-motor. As the pinion gear moves out on the shaft, it becomes meshed with the flywheel ring teeth. Now the starter motor is driving the flywheel through the pinion gear. When the engine starts, the spinning flywheel ring gear will "spin" the pinion gear back down the threaded shaft out of the way of the flywheel ring gear.

The starter is mounted securely to the engine by mounting flanges on either the side or end of the starter. Since the engine block may be made of cast aluminum and the size of the starter motor may be small, the mounting bolts may be a problem. If a targe wrench is used, the bolts may easily be overtightened and the threads stripped.

Also, because of the vibration encountered, the bolts may become loose. If the bolts become loose, the starter will not make a good electrical connection to the engine ground or may allow the pinion gear to move away from the flywheel ring gear causing improper meshing of the gear teeth.

Bendix drives may fail because of dirt, wear, or improper mounting. Dirty and worn Bendix drive units usually allow the starter motor to spin free without engaging the flywheel. The Bendix drive is easily replaced.

If the starter is not mounted firmly or not correctly aligned, the pinion gear may bind when meshing with the flywheel ring gear causing starter drag. This will cause slow starter operation or will cause the starter to be locked completely.

ELECTRIC STARTER TESTS

Starter circuits can be quickly checked with a D.C. voltmeter for the voltmeter can be connected without disconnecting any circuit components.

First, test the battery voltage. Connect the voltmeter as shown in Test 1. Observe the battery voltage. It should be either 6.3 volts or 12.6 volts. Record the reading below. Push the starter switch and observe the battery voltage. Record the reading.

TEST 1 Battery voltage with no load____________

Battery voltage with starter switch being held.____________

If the battery voltage remains the same or falls very little and the starter fails to crank the engine, either the switch, starter, or wiring is not making a complete circuit connection. Continue with voltmeter Tests 2, 3, 4, and 5.

If the battery voltage falls below 4 volts for a 6-volt battery or 8 volts for a 12-volt battery, either the battery is not up or a short exists in the starter circuit. Test the battery. (See Battery Tests.)

TEST 2 Meter reading with no load____________

Meter reading with starter switch being held_____________

Test 2 checks the switch and cables. Before cranking, the voltmeter will read the battery voltage, the same as Test 1. When the starter switch is engaged, the voltmeter should drop to zero or less than one-half volt. If the voltmeter does not drop down when the switch is engaged, a loss is occurring in the switch or cables.

TEST 3 Voltage across switch before contact_____________

Voltage across switch with switch being held_____________

To check the switch only, connect the voltmeter across the switch terminals as shown in Test 3. Again, the meter will read the battery voltage until the switch is engaged. When the switch is engaged, the meter should drop to near zero volts. Failure to drop to less than one-half volt indicates a bad switch.

If Test 2 showed a loss that Test 3 did not show, the loss occurred in a cable or connection. Tests 4, 5, and 6 will show cable loss while cranking. Any reading indicates loss. Locate the loss and correct it. Corroded terminals or bad connections could cause loss. Test as shown in Tests 7 and 8. These tests are made with the starter switch engaged. Any reading indicates loss,

STARTER-GENERATOR

The operation of the combination starter-generator refers to the purpose of the cutout relay in the regulator unit. When the output voltage of the generator becomes less than the voltage of the battery, the current stops flowing in the direction that charges the battery arid it begins to How back through the generator armature winding.

The field and the armature are both now battery powered. The magnetic fields produced by the field windings and the armature are now like magnetic poles and are therefore repelling each other causing the armature to attempt to turn to align the magnets. The generator is now acting as a motor. During generator operation the cutout relay opens when the generator output falls and it prevents the generator from "motoring."

A starter switch connected to bypass the cutout relay makes the generator become a starter motor when desired. The starter switch connects the armature directly to the battery plus while the other armature brush is connected directly to the engine ground (battery negative). This makes both the field windings and the armature winding full strength for maximum starting torque.

The starter-generator is usually belt driven to the engine. The engine pulley is larger to decrease the speed and increase turning torque whiie starting. The belt must be kept at correct tightness to crank the engine satisfactorily. Once the engine starts, the generator and regulator operate as described in the generator section.

A solenoid switch and ignition key may be used instead of the heavy starter switch. Keep in mind hen; that since a great deal of power is needed to crank the engine, heavy current flow is needed in the starter switch circuit. On the solenoid switch the starter switch is engaged electrically. The ignition key engages the starter switch.

Notice that the ignition key in the START position connects the solenoid coil to the battery positive for cranking. In the OFF position the key shorts the ignition primary winding to the engine ground and prevents the points from creaiing a spark and thus stops the engine. (See Ignition section.) Caution: This switch cannot be replaced with an automotive switch because an automotive switch connects the ignition terminal to the battery positive instead of to the ground. The magneto and switch would be burned out immediately.

The ammeter is also bypassed during the cranking operation and will not read the cranking current. The current needed for cranking is in excess of the capability of the meter and would cause meter damage. The charge from the regulator to the battery will show on the ammeter, as will flow from the battery to an accessory load. On some units there is an accessory terminal on the regulator.

STARTER-GENERATOR TESTS

Starter-generator units are tested as separate units. The charging function is tested as any generator unit. (See Generator Tests.) On these units it is usually advisable to check the starter function first since the starter and generator are the same unit. If it will crank the engine, then it should also charge and if it will crank the engine but will not charge, the problem is likely in the external wiring or the regulator unit.

A frequent cause of failure of these systems is the drive belt. Check the pulleys to make sure that a smooth vee belt has not been placed on a unit designed for a notched belt. Check the belt tightness. It should not deflect more than one-quarter of an inch with normal thumb pressure. If the belt has been slipping and has become glazed, replace it. The new belt will need retightening after a few hours of operation and certainly after each operating season. If the unit is used two seasons such as mowing in summer and snow plowing in winter, the belt tightness should be checked each season.

VOLTMETER BATTERY TEST

Indication of starting or charging problems may be detected by connecting a D.C. voltmeter to the battery as shown on the next page. When connected to a battery on a unit not running, the voltmeter should read 12.6 or 6.3 volts indicating a normal battery voltage. Observe the voltmeter carefully while cranking the engine. The meter should stay above 4 volts for a 6-volt battery and above 8 volts for a 12-volt battery. Once the engine is running, the voltmeter will indicate charging voltage. If the battery comes above the initial reading of 6.3 or 12.6 volts, the unit is charging. The amount of charge will be indicated on the ammeter if there is one. If there ,sn't an ammeter, one can be connected as shown by placing it in the battery cable at the regulator battery terminal. At half throttle, voltage readings should not exceed 7.5 volts or IS volts.

PROBLEM	CAUSE
Starter spins but does not turn engine.	Loose belt. Glazed belt. Wrong type belt.
Battery does not stay fully charged.	Loose belt. Recharge battery. If starter functions OK, fault is in wiring or regulator. See Generator Test section. Test as for any generator.
Battery stays fully charged but will not crank or cranks slowly.	Problem in the starter switch circuit. Check starter switch and wiring as described in Starter Test section.
Voltage drops below 4 volts on a 6-vott system or 8 volts on !2-volt system when cranking.	Battery defective or not fully charged. Starter shorted.
Battery voltage remains unchanged when starter switch is pushed. Charging circuit OK.	Defective starter switch, loose or corroded connection, defective ground on battery or starter.
Battery voltage drops too low when cranked. Voltage does not rise above battery normal after engine starts.	Battery discharged because of no charging circuit output. Check charging circuit. See Generator Tests.

Adapted from:

SMALL GAS ENGINES

James A. Gray and Richard W. Barrow

School of Technology Indiana State Univetsitv

Prentice-Hall, Inc., Englewood Cliffs, New Jersey

Drawings by Robert F. MacFarlane

Retrieved from the CD3WD project.
Rebuilt and re-compiled to be useable by Autonopedia

Autonopedia