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Starter trouble

Q: Why is my starter becoming unreliable?

A: A starter is a relatively simple electric motor, but many things can cause it to fail or work intermittently. Here are just a few. Keep in mind that all starters are not constructed alike, and some of this discussion and terminology may not be appropriate to your starter. I’m just talking about a few basics.

One of the most common causes for problems is as simple as faulty grounding. In order for DC electricity to flow through the starter components with sufficient power to turn over your engine, all of the contacts must be good. Of course, a corroded positive contact, whether on the battery end or the starter end (or anywhere else in the line), can cause the problem. But the problem is more likely to occur in the negative wire, because this wire often is not inspected, and the contacts (as well as the wire itself) may be in less-friendly areas.

For example, the ground for the starter sometimes isn’t via a separate ground wire back to the battery or a negative stud. Instead, it’s through the engine block itself. The starter is bolted to the engine, making contact at that point, and the engine block is connected to the battery by a heavy gauge wire bolted to the block. This wire often is bolted on a lower part of the engine, where it’s hard to see and is less likely to be inspected. And it’s often relatively close to the bilge and, therefore, not only hard to inspect but also prone to corrosion.

Even if you do inspect it, it could look fine, but there may be corrosion between the terminal on the end of the wire and the block. This corrosion, while allowing smaller amounts of current to pass through the contacts, may impede current flow enough to interfere with the starter’s performance, which requires a much stronger flow.

If your starter is giving you trouble, one of the first things to do is check the wire terminals on your starting battery. But you should also find the negative cable contact point on the block, unbolt it, clean the terminal and its contact point, spray on a good water-dispersing lubricant made for the purpose, and put it back together.

Another frequent cause of starter problems is usually more difficult to diagnose and solve. Without going into too many details, it essentially involves impaired contact points where the brushes transfer power to the commutator ring. For example, there may be a low spot or damaged area in the commutator ring, which could impair contact as the brush passes over that spot. If the starter, at its last use, happened to stop at that spot, it may have difficulty turning over the engine because the impaired contact between the brush and that part of the commutator ring results in insufficient power to the starter. The flaw could be caused by various things, including old age, voltage problems and contact with the brush holder should it’s retainer break or become dislodged, or should the brush become too worn. This problem can be hard to diagnose because it is intermittent. Also, it generally requires repair by a shop or a new starter, depending on cost effectiveness.

The third big area is in the solenoid. (I covered solenoids in my May 2007 Q&A. Search the story archives at www.Sound Keyword: solenoid) If the relay contacts in the solenoid are impaired, the starter will perform poorly because this impairs the flow of electricity to the starter. Arcing over time will cause impairment. Arcing occurs as part of normal wear and eventually burns the contacts and deposits carbon on the contact surfaces. You won’t see it because it occurs within the solenoid — a good reason to keep a spare. If the solenoid has been “hanging up,” or not operating freely, there is more likely to be arcing and burning of contacts. This can be caused by such problems as grease or rust in the cylinder or damage to the coils inside the solenoid.

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This article originally appeared in the August 2008 issue.