DIAGNOSE THAT COREOne of the most typical mistakes humans make, is failing to see the most important facts that are strategically located right under their noses. For some reason, the most ignored tools are the ones that present themselves most obviously. This enigma seems to be embedded deep within in our genetic codes, and inherited down through the ages in the form of some type of unrecognizable curse, since the times of cavemen inventing the wheel. Today, for this short moment, in this small category, we plan our escape.

When you take your starter off your vehicle, it becomes the most valuable diagnostic tool that you could ever have.

1. Copper Post

Many, many thousands of starters in the world today suffer from one main affliction : Low voltage. Low voltage can happen because of resistance (corrosion) anywhere on the entire circuit of connectors, clamps, cables and eyelets or can simply be low voltage from an older battery. Another cause of resistance that very few people are aware of is the effect that thermal cycle has on metals that are dis-similar.

The starter can produce evidence that there was a bad connection on the large copper solenoid post. Remove the nut and the cables from the solenoid stud. You can find the solenoid stud easily because that’s the one the main cable from the battery goes to. Note very closely the threads on the copper stud. Often you will notice 4 or 5 threads that are brown or a darker copper color.


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Electrons flow from the face of the battery cable eyelet to the face of the nut. Then from the nut, they go to the copper stud through the threads of the nut. It is these threads (the ones between the copper stud and the top tightening nut) that most often becomes a bad connection area. Thus, the heat. Thus the discolored threads. Thus, the voltage drop. This is why dielectric grease is so important to all the copper studs when installing a new starter.

2. Inside the solenoid

When a high current switch is discontinuing its duty cycle (when you’re done cranking the starter and you turn your ignition switch off) there is an arc where the bridging contact moves away from the stationary source of high current. The arc is much greater on the source contact, than on the load contact. The size of the arc depends on the amount of current that was flowing. This is why inside a solenoid, the battery side is always worn much more that the motor side.

Each and every time current flow is stopped, there is a minute amount of copper that is dissipated (burnt up) in the arc. The higher the current, the more copper is lost. The size of the arc is directly proportional to the amount of current that was present at this point in time. The arc could even be considered an amperage fingerprint. Because of a wet cell battery’s tendency to self regulate a higher current when subjected to a low voltage, it is actually easy to see by observing the solenoid contacts, what condition the users voltage situation was, at the time the arc was made.

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Extreme cases of low voltage to the starter are even more obvious because there are large black arcs present. You can’t say why the starter had low voltage because there are a variety of causes, even overcrank, but you can say for sure, that the starter had low voltage, and know that the situation must be corrected.

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These are examples of normal amperage flow (no voltage drop).

3. The bendix

A bendix can also have a story to tell about the condition of the flywheel and occasionally, how it got that way. Look carefully in the pocket that the bendix rides in. Sometimes you can find metal shavings or splinters. Take a magnet and wipe around the inside of the bendix aluminum housing and see if it picks up any metal splinters. If it does, look extremely hard at the bendix. Are there any chips off it ? If there are, a new bendix will correct this situation. If there are splinters and the bendix appears to be un damaged, the splinters must be from the flywheel. A new bendix will not correct OR help engagement problems.

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If you are not experiencing any flywheel engagement problems and found shavings or splinters in the starter, refer to the maintenance on a damaged flywheel section of this website. If you are experiencing flywheel engagement problems and found shavings or splinters in the bendix pocket, you may need to consider a new flywheel installation along with the new starter.

4. Pollutants (oil or antifreeze)

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Mainly, only oils or transmission fluids are located low enough to gain entry into a starter. Oil can work its way into even the smallest crevice in a starter. Once its in, its pretty much over. Oil breaks down the copper/carbon content of the brush. Combined with arc, the brushes practically disintegrate at an unusually fast rate, even if oil is just ambient. This is why its a waste of time to try to seal the starter with RTV silicone instead of fixing the actual leak.

5. Burnt smell (overcranked)

Once there was a wise and savvy mail man. This particular mail man had been around the block more than a” time or two” and unfortunately, had a wealth of experience with one of the mailman’s most famous occupational hazzards : dogs. One particular day on his route, he encountered the familiar barking, snarling dog. As he stood there accessing the predicament, the dog’s owner appeared at the door way of the home and announced, ” Don’t worry, he doesn’t bite. ” To this the savvy mailman replied ” Does he have teeth ? ” The owner reluctantly nodded their head, yes. ” Then he bites.”

He was right. A smart @$$! but, he was undeniably correct with logical reasoning. This undeniable reasoning is applicable when you open up a starter and you smell that super strong burnt odor. There’s only one way that a starter can get that way. Not a short some where, not an open somewhere, only from cranking (doing its job) for an extended period of time. Technicians and mechanics must tactfully explain the meaning of overcrank and proper use to the customer or friend. Never blame or accuse a person of not knowing how to start their car. Just explain the 10 seconds crank, 30 seconds wait, rule as outlined in the section on use and abuse, and how to diagnose if the cause of the burnt starter might be ignition switch/ wiring related.

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Armature has been burnt from overcrank.  A strong burnt smell will be present.

6. Clutch presence


When the clutch is near failure much of the dust will collect in the bendix pocket. This can ruin a flywheel because if any friction material lodges on the shaft that the bendix travels in and out on, it can cause the bendix to hang in the flywheel after the engine has started. This can crack or chip the flywheel, not to mention the damage that can occur to the starter. The owner of the vehicle should begin to make plans to inspect the clutch wear, or make arrangements to eliminate the driver with ” a heavy left foot “.

7. Cracked nose cone


Look very closely for cracks in the aluminum housing. These could indicate the starter should have had a shim with the previous installation, and that it might be a good idea to install an extra 1/32″ shim on the present installation.

8. Broken drive end housing or bendix gear.

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If a starter had enough torque to break it’s own drive end housing, it would never make it off the dealership parking lot. The aluminum structural design has to be strong enough to withstand the torque produced by the starter, or the structure would collapse every time you tried to start your car. This is just a simple fact : a starter cannot under its own power develop or produce enough torque to break its own structure.

So, after knowing that, you might ask, ” How does it break then ? ” The answer is ” Engine kick back ” also known as hydro lock, backfire, roll back or whatever makes an engine go backwards. This is an extremely rare condition nowadays, and is considered next to impossible for many vehicles BUT it does occur. If there is gas vapor present in a cylinder (such as a leaky injector or o-ring) and the cylinder is BTDC, the next time the plug fires, it’s going to reverse rotation. It’s pure fact.

The evidence of this occurrence may not be on the surface of the starter. Planetary gear reduction starters of today have a plastic external stationary gear that will strip or shatter. However, if you have a starter that shattered or stripped this gear, it should not be considered hard evidence of kickback, like you should consider it with a mutilated drive end housing and bendix. The main point here is this : Don’t just re install the starter unless you plan on doing it on a regular basis. Whatever happened will most likely happen again. Most part stores and rebuilders won’t warranty a kick back destroyed starter. And if you want to rebuild it yourself, you’re wasting your time. The core is most likely no good.

9. Magnification of the motor stud connection.

Remove the nut on the motor stud. You can find the motor stud easily because it contains the large wire going inside the starter.


Remove the large wire from the stud and observe it closely for discoloration. Also observe the copper motor stud the same way as described in section 1. Often there are darker colors or black threads that indicate resistance heat. Look at the eyelet of the cable that goes into the starter with a magnification glass. It is not uncommon to find small arcs where there was bad connection. This would cause the symptom “Sometimes I turn my key and nothing happens.”



Good condition.  This is not a failure point.



You can see the arcs.  This causes the symptom “sometimes I turn my key and nothing happens”.

Notice the dark marks on this Ford starter with a 5.4L engine. You can even notice arcs on the back side of the ear indicating that it had a bad ground. If you saw this starter in action, you would notice sparks flying out of the bolts holding it on the block. It is imperitve on the 5.4L to clean the mounting bolts and apply white lith. to the threads.


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