Starting system troubleshooting

borrowed from Jack hunt copyright to Jack Hunt

This is designed to help you in troubleshooting your starting system. These are not by any means all the possible causes of hard starting, but the most common ones are listed here. Some problems can have more than one cause, some causes have more than one symptom. You may have more than one problem occurring at the same time. Each time you find something wrong, fix it and start over.

Tools needed:

Index of Symptoms
Cranks Slowly
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Clicks but won't crank over
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Won't even click
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Cranks over but won't start
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Dead or Discharged Battery

Before undertaking any testing procedures, made a careful visual inspection of the battery to check for defects. What you see can be very useful as well as important when analyzing test readings. Follows the inspection procedure outlined below.

    1. Make sure the filler/vent cap holes are not plugged.
    2. Check the battery case top for dirt and electrolyte; This will cause excessive self-discharge and should be removed. To illustrate this point, put the negative lead of your voltmeter on the negative battery terminal. Touch the positive lead to a wet or dirty spot on the battery top. If you get any voltage reading, the battery is slowly discharging through the contamination on top of the battery case.
    3. Look for raised cell covers or a warped battery case. Either of these indicates the battery has been overheated or overcharged.
    4. Check battery terminals, clamps and cables for loose connections, corrosion, etc.
    5. Make sure the battery is the correct battery for you application. It is possible that a previous owner has installed a battery with insufficient capacity for your application.
    6. Inspect the battery case for cracks and leaks.
    7. Remove the filler/vent caps and check electrolyte levels. If it is below the top of the plates, add water. If it is low, but not below the plate level, test cells with a hydrometer before adding water.
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Weak Cell in Battery

Measuring the Specific Gravity

A battery hydrometer is used to measure the specific gravity of the electrolyte. This instrument indicates how much unused sulphuric acid remains in the electrolyte and thus determines the battery's state of charge. The hydrometer used should be graduated in 0.005 intervals of specific gravity from 1.160 to 1.320; markings should be accurate to within 0.002 specific gravity. To test specific gravity with a hydrometer:

  1. Remove the filler/vent cap from each battery cell.
  2. Insert the tube at the bottom of the tester into each cell in turn.
  3. Hold the hydrometer vertically and squeeze the rubber bulb gently, then release it. This will draw sufficient electrolyte into the tester barrel to float the test gauge freely.
  4. Withdraw the hydrometer from the cell and hold in a vertical position at eye level so that the float stands free of the barrel sides.
  5. Read the float scale at the point where the surface of the liquid meets it. With some hydrometer designs, surface tension can cause a curvature of the liquid against the float--disregard any curvature or the reading will be incorrect.
Interpreting the results:

All readings must be adjusted for temperature.

Any reading below 1.220 indicates a poor charge condition. Below 1.150 means that, for all practical purposes, the cell is dead. If the reading of any one cell is lower than the others by 0.50 or more, that particular cell is shorted and the battery will have to be replaced.

When all cells test in the 1.220 or below range, the battery should be recharged with a charging unit, leaving the filler/vent caps loose or completely off. The cells can be tested during the charging to determine when the process is complete. When the specific gravity remains the same in three successive readings taken an hour apart, and all cells are expelling gas (or the electrolyte is bubbling), the battery has accepted as much of a charge as it can hold. The expelled gas (hydrogen) is highly explosive; do not smoke, create sparks or bring an open flame near the battery. To determine the actual specific gravity at this point, it is necessary to let the battery sit, off-charge, for an hour before taking another hydrometer reading. If charging does not bring the battery cells up to at least a 50% charge, the battery will have to be replaced.

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Transmission not in Neutral

Did you check? It happens.

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Ignition Switch Off or Kill Switch Engaged

Hey, it happens. I won't tell anybody if you won't.

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Battery Theory

Automotive and motorcycle batteries consist of six individual cells, each a battery in itself producing approximately 2 volts, depending upon its state of charge. The cells contain a number of positive and negative plates of lead which react chemically with battery electrolyte in such a way that there is a flow of electrons set up between the plates. Cells are connected in series--the negative terminal of one cell is joined to the positive terminal of the next, and so on. This produces a voltage output for the entire battery equal to the sum of that produced by the individual cells. The positive pole of the first cell and the negative pole of the last provide the terminals to which the battery cables are attached. Each cell is separated from the others so that there is no mixing of electrolyte from cell to cell. As battery current is used, the sponge lead of the negative plates is partially converted into crystalline normal lead sulphate, while the lead dioxide of the positive plates is converted to lead sulphate. When all the available electrolyte acid has been absorbed into the chemical structure of the plates, the battery becomes fully discharged. But directing current into the battery cells reverses the chemical reaction by driving sulphuric acid from the plates and increasing the acid content of the electrolyte. Once this is accomplished, the battery is ready to start producing current again. In actual practice, the electrolyte is kept at a steady state of acidity by the current delivered to it by the alternator. After running the starting motor, the amount of acid in the electrolyte is low, because the heavy demand for current has caused it to be absorbed into the plates. Because the voltage of the battery is low, current will flow from the alternator into the battery.

Note do not charge a battery at anything more than 2 amps

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Temperature Correction

As ambient temperature increases, the battery electrolyte expands, reducing the specific gravity; as temperature decreases, the electrolyte contracts and the specific gravity increases. Battery Hydrometer readings are considered as correct when the electrolyte temperature is 80F. For each 10 degrees above 80 degrees Fahrenheit, you must add 0.004 (also known as four points of gravity) to the original reading; for each 10 degrees below 80, you must subtract 0.004 from the reading. Unless these variations in specific gravity and temperature are taken into consideration, the hydrometer reading will provide only an approximate indication of the amount of acid in the electrolyte when its temperature is other than 80F. Temperature correction can be made by taking the temperature of the electrolyte with a battery immersion thermometer before taking the specific gravity reading or by using a hydrometer equipped with a thermometer.

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Voltage Drop in Starting Circuit

Connections in a high amperage circuit such as a starter can do strange things. They can appear to be clean and tight, yet at the same time they can be the cause of a starting system failure. A dirty or loose connection will pass 12 volts (nominal) through it at low amperage with little or no current loss, yet at higher loads it will not be able to handle the amperage and the starter will either turn too slowly to start the engine, or won't turn at all.

Fortunately, a loose or dirty connection has a few distinct characteristics that makes it easy to spot--if you know what to look for.

Any time there is a bad connection, there will be a voltage drop across it. Electricity is never "lost", it is simply converted to another form of energy, be it light, heat, motion, etc, or a combination of two or more. Loose connections in a starting circuit will get hot almost invariably when subjected to high current loads, such as attempting to start (heat). A very bad connection will arc (light). Touching a very hot connection will make one draw one's hand back quickly (motion). :-)

Voltage drop is measured by placing one lead of the volt meter on one part of the connection (i.e. the battery post) and the other lead on the other part of the connection (i.e. the battery cable connector). When the engine is cranked over, the voltmeter will read voltage if there is resistance in the connection. Any connection is considered "bad" if there is more than .2 volts showing across the connection while cranking. There should not be more than .5 volts total loss from the positive post of the battery to the starter motor connection. This includes the starter solenoid as well as all cable connections.

To do a voltage drop test, first remove the necessary body panels to expose both terminals of the battery. Set the voltmeter on a low scale (3-5 volts DC is good). Put the negative lead of the meter on the negative battery post and put the positive lead on the negative battery cable end. Crank the engine with the kill switch engaged to keep the engine from starting. The reading on the voltmeter should be .2 volts or less. If it is more than .2 volts, remove the connection, clean it, and tighten it securely. Repeat the test until results are satisfactory, then connect the negative voltmeter lead to the negative battery cable end, and the positive voltmeter lead to the other end of the negative cable. Crank again. If the reading is not within specs, remove and clean the connection and test again. When the test results are satisfactory, put the negative voltmeter lead on the frame end of the negative battery lead, and put the positive voltmeter lead on a good frame ground. Crank again. If the reading is not within specs, remove and clean the connection and test again.

Testing the positive side of the circuit is similar. Start with the positive battery post and the cable connector, this time put the positive lead of the voltmeter on the positive battery post and put the negative lead of the voltmeter on the connector of the positive battery cable. Crank and repair as necessary as above. Repeat the sequence for every single connection down the line all the way to the starter motor. Remember to check the connection between crimped terminals and the actual cable. Corrosion can set up inside a crimped connector and make it useless even though it looks clean and tight on the outside. Use the sharp point on the voltmeter probe to puncture the insulation of the cable when doing a voltage drop test on terminal ends.

When testing from one terminal of the solenoid to the other, the voltmeter will read full battery voltage until the starter switch is pressed. For this reason one should do one of the following:

  1. Set the voltmeter to a scale of 12 volts or more until the starter is engaged, then switch to a lower scale to read voltage drop across the solenoid, or:
  2. Have an assistant to crank the engine, and make the voltmeter connection after the starter has engaged.
In either case, set the voltmeter to a scale of 12 volts or more, or remove the voltmeter connection prior to stopping cranking to avoid damage to the voltmeter.

A voltage drop of more than .2 volts across the starter solenoid calls for the repair or replacement of the solenoid.

Total starting circuit voltage drop is measured from the positive battery post to the terminal on the starter motor. This connection will read full battery voltage when connected, but should show less than .5 volts while cranking. Any reading over .5 volts indicates a voltage drop somewhere in the starting circuit which must be repaired.