Starting System Components

The battery is the first place to look when a vehicle has a slow start or no start condition. Check the battery posts and terminals. Make sure they’re free of corrosion, and that the terminals are firmly fastened to the posts.

Starting system circuit and components.

Battery: Perform a voltage test using a voltage meter. A good battery will have 12.6 volts. This is because there are 6 cells in series at 2.1 volts each. A specific gravity test is performed with a hydrometer. A fully charged battery will have a specific gravity of 1.265 at 80° F. Perform a battery load test to see if service or replacement is necessary. First determine the load by retrieving the CCA from the battery case and reducing this number by half. The test discharge rate is one half of the batteries cold cranking rating. Apply this load to the battery for 15 seconds. Battery voltage must remain above 9.6 volts at 70° F.

Battery Cables: Perform voltage drop tests on the starter and ground cables. A loose or corroded ground connection between the engine block and battery negative cable will cause a sluggish or no start condition. Battery cables come in different gauges. Years ago battery cables were 6 gauge, because there weren’t so many accessories requiring higher amperage. Today's vehicles often come with factory 2 and 4 gauge battery cables, capable of handling higher rates of current. A 2 gauge cable is thicker and can handle more current than a 6 gauge cable.

Solenoid and Starter Motor: A starter solenoid is an electromagnetic device that serves two purposes: it completes the circuit between the battery and the starter motor, and moves the starter’s gear into mesh with the engine’s ring gear. The starter motor will wear, causing high current draw. Typically the starter motor is removed and replaced, but internal components like brushes, windings, and bushings may be replaced and the starter placed back into service.