Starting System Components
If the vehicle will not crank or turn over the first place to look would be the condition or charge state of the battery. Visually check the battery posts and terminals. Make sure the connection is free of corrosion and the terminals are firmly fastened to the posts.
Battery Cables: Check the condition of the battery cables and perform voltage drop tests on the starter and ground cables. Battery cables come in different gauges. Years ago battery cables were 6 gauge because there weren't so many accessories requiring higher amperage. Vehicles often come factory with 2 and 4 gauge battery cables capable of handling higher rates of current. The lower the gauge number the thicker the cable. For instance a 2 gauge cable is thicker than a 4 gauge cable.
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 using a hydrometer. A fully charged battery will have a specific gravity of 1.265 at 80F. 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. The batteries voltage must remain above 9.6 volts at 70° F.
Switches: The neutral safety switch and clutch safety switch are used to prevent startup during undesired situations. A neutral safety switch will prevent starter engagement in all gears except park and neutral. The clutch switch requires that the clutch pedal be depressed before starting the vehicle. Both of these switches can be tested with an ohmmeter. Also check the ignition switch to make sure it provides power to the starting circuit when placed in the start position. Starter Relays are devices that use low current to control the high current required to turn the starter.
Solenoid and Starter Motor: A starter solenoid is an electromagnetic device that serves two purposes. It competes the circuit between the battery and the starter motor. It also moves the starters gear into mesh with the engines ring gear. The starter will wear causing high current draw and parts like the brushes, windings, and bushings must be replaced. Compare the amperage required to turn the starter against manufactures specifications using an ammeter to check current.
