Starter Replacement and Diagnosis

Starters and alternators

Rotating electrical parts such as starters and alternators often have to be replaced on older, high-mileage vehicles. Fuel injection has helped prolong the service life of starters by allowing engines to start more quickly when they are cranked. Such is not the case with alternators.  

Battery problems with starters

A starter that’s failing may crank the engine too slowly for a quick start, or it may not crank the engine at all. Often, the problem is not the starter but a low battery or a loose or corroded battery cable connection. So, check the battery charge and condition first. A good battery should be capable of accepting and holding a charge from a battery charger, and should be at least 75 percent charged (12.5 volts or higher). If the battery’s voltage is low and it doesn’t take a charge, you need a new battery. Load-testing the battery or using a conductance tester to check its ability to take and store a charge can also confirm the need for replacing the battery. The average service life of a car battery is only about four to five years, and can be shorter in hot climates. At AutoMetrics, we have noticed batteries not lasting as long as they used to due to Chinese lead. So also consider the age of the battery when evaluating its condition.  If the starter passes the tests, the slow-cranking or no-cranking problem is obviously something other than the starter.

The best diagnosis

We will check the battery, battery cables, starter relay and the starter circuit and wiring connections for possible faults. If the starter fails the tests due to low cranking RPMs, excessive current draw or it fails to spin at all, then starter replacement will be needed. High resistance within the starter itself, worn brushes, or grounds or opens in the armature or coil windings can cause excessive current draw. It can also result from increased internal friction due to shaft bushings that bind or an armature or magnets that are rubbing inside the starter.

Loose starters

A loose starter may crank an engine slowly, noisily or not at all. Loose bolts will make for a weak ground connection. The starter may also flop around, slip, chatter or fail to engage depending on how loose it is.

The starter drive

Sometimes the engine won’t crank even though the starter will spin. This is usually an engagement problem due to a weak solenoid or a defective starter drive. A starter drive that is on the verge of failure may engage briefly but then slip. The starter drive has a one way overrunning clutch mechanism that you can check once the starter is out of the car (and replace if necessary). The drive should turn freely in one direction but not in the other if good. A bad drive will turn freely in both directions or not at all. If a drive locks up, it can over-rev and destroy the starter. We can diagnose and repair it right at AutoMetrics.