ONE DAY IT JUST happens. The magic in your starter has disappeared and you're left with about two tons of lifeless iron and a helpless feeling. About this time you might be wishing you knew a little more about troubleshooting starters.

Your starter problems can be electrical and/or mechanical in nature. What you see, hear and observe should lead you in the right direction toward solving the problem. Take note of the symptoms to help you formulate a plan toward obtaining a solution.

Do you have to crank the starter several times before it eventually gets the engine to turn over? Does the starter drive unit makes a grinding noise when cranking the engine? What should you do if everything is silent and you have no real clues? Where do you start your diagnosis?

To help solve any starter mysteries, the best tool to have: Asa volt/amp meter, however, a simple test light can get you a long way, if you don’t have a volt meter. Make your first check with either device at the battery. Obviously the condition of the battery is the key to the health of the starting system. After you measure the amount of voltage at the battery, then check for battery voltage along the path to the starter switch to determine if current is indeed reaching that point. Although the test light will confirm whether there is current, a volt meter will identify how much current is present.

To begin, a healthy six-volt system should have seven volts present at the battery and at the battery terminal of the starter. A 12-volt system should have 13.5 to 14 volts available at these locations.

The purpose of this test is to determine the presence of high resistance in the starting circuit. Before you begin this test, pull the coil wire so the engine will not start when performing the tests.

Place one test lead of the volt meter (or test light if that’s what you are using) on the positive post of the battery and the other test lead at the battery terminal on the starter switch or solenoid. (Most pre-WWII vehicles will not have a solenoid.) With the engine cranking, there should be less than %-volt drop from the battery voltage. If the voltage drop is greater, check the battery cable for damage while also checking for poor connections. If you can’t correct the drop in voltage, replace the cable.

Next, disconnect the volt meter and then make the connections to the negative post of the battery and the starter housing. While the engine is being cranked, loss of voltage should again be less than % volt. If it is greater, there is a problem with the ground cable or the negative pathway returning to the battery. Again, if corrections can’t be made by cleaning and tightening connections, replace the cable.

If your vehicle has a solenoid, place one volt meter lead on the solenoid battery terminal and the other on the solenoid motor terminal. Crank the engine again and take note if the drop is more than % volt. If there is a voltage drop of % volt or more between the solenoid battery terminal and the solenoid motor terminal, this indicates a problem with the starter solenoid. The most common problems are worn or broken parts inside the solenoid that block the path of current to the starter.

When the solenoid or starter switch fails to engage the starter motor drive, the problem most often is related to low voltage caused by high resistance in the starting circuit. To check for this condition, connect one test lead of the volt meter to the battery terminal of the solenoid and the other terminal to the S terminal of the solenoid. If the voltage drop is greater than 3.5 volts when cranking the engine, there is excessive resistance in the solenoid control circuit. If the electrical connections are clean and solid, the problem is most likely a defective solenoid.

If the voltage drop is less than 3.5 volts, but the solenoid still does not pull in the magnetic plunger that completes the circuit, measure the voltage available at the S terminal of the solenoid. There should be a minimum of 7.8 volts present when testing a 12-volt system. A functioning solenoid should engage with 7.8 volts or more (a possible exception is when it is warm from excessive heat).

TERMINAL IDENTIFICATION

Most starter switches and solenoids have terminals marked with letter designations as follows:

• The battery terminal is marked B. This is the connection from the positive terminal of the battery.

• The motor terminal is marked M and is connected internally to the starter, most commonly with a flat copper bar or heavy cable. Only solenoid-type switches mounted on top of the starter use an M terminal.

• The I terminal is where the ignition switch is connected to the starter.

• The starter switch, labeled S, allows full battery current to reach the ignition coil during starting. The S terminal is hot only during the cranking of the engine. It applies full battery voltage to the ignition circuit, bypassing the ballast resistor.

After starting, the ignition receives normal system voltage through the ballast resistor. After completing these tests, if the starter is still not performing properly, check the internal parts of the starter. To begin, your volt/amp meter will identify if your starter is drawing excessive amperage. Connect your test leads to the B terminal on the starter and to a ground (usually the starter case). The starters on most six-volt systems should draw about 250 amps (consult your service manual for an exact figure). If your amp reading shows more than a 50-amp increase, your starter probably needs attention; internal parts are probably worn or defective. A 12-volt starter typically requires about 175 amps and again, if your test indicates an additional draw in excess of 50 amps, you probably have an internal starter problem. Excessive amperage or failure to start the engine can often be traced to worn bearings or bushings, a bent armature shaft, broken pole shoes or magnets, or a damaged motor drive unit. Remove the inspection cover at the rear of the starter for a visual inspection of the brushes. Brushes are about one inch long when new. If they are worn to %-inch, it’s unlikely that enough electrical current passes through them to allow the starter to function properly. Also, look for broken brush springs or an excessively dirty or burnt commutator — an indication the armature needs attention. Worn bearings or bushings allow the armature to drag on the field coils. You might notice carbon dust or metal shavings that indicate problems. When you find these indicators, it means your starter is a prime candidate for a rebuild.

To examine the starter drive unit, begin by looking for engine oil that has dripped on the motor drive shaft. Oil mixed with dirt and grime sometimes prevents the starter drive from fully engaging the flywheel. If the starter does not engage the flywheel, it will usually make a whirring noise. If it partially engages the flywheel, there will be a clashing noise.

The same problem can prevent the motor drive unit from disengaging the flywheel, resulting in a damaged unit. If you disassemble and clean the shaft, the problem is often corrected. Sometimes this will expose a worn clutch mechanism or shaft, which is an indicator that the motor drive needs replacing. Although it may be tempting to do so, it is not necessary to lubricate the starter drive. It is lubricated internally during manufacture.

The starter motor drive unit is not serviceable and should be replaced when an inspection reveals the drive teeth have become worn or the clutch mechanism fails to slide easily on the armature shaft.

In rare instances the flywheel can be damaged — sometimes from a backfire or from a defective starter motor drive that has been ignored too long. By removing a cover on the bottom side of the engine a visual inspection of the flywheel can reveal bent, broken or missing teeth. Sometimes the flywheel can be bent, which causes an alignment problem with the starter drive and will eventually damage the starter.

As with most things mechanical, it is always better to repair a defect at the first sign of trouble. Ignored problems do not fix themselves, and instead they lead to more problems that are generally more expensive to fix than the original one.