Aftermarket April 2022

52 AFTERMARKET APRIL 2022 ROTATING ELECTRICS www.aftermarketonline.net Commenting on what can go wrong with a starter, and how to fix it, DENSO Europe Pan European Strategic Marketing Manager Fatiha Laauich said: “If the battery is in good condition, but the starter does not crank the engine, the problem could be a poor ignition switch connection or excessive resistance in the starter control circuit that can reduce the voltage available to the magnetic switch. The pinion gear not engaging or engaging incorrectly are both symptoms of this problem. “Excessive resistance could occur at the ignition switch contacts, park/neutral start switch, clutch start switch or the circuit wiring and connections. So, perform the following voltage drop tests to isolate the cause and repair the fault; Connect the voltmeter positive lead to the positive battery terminal and the voltmeter negative lead to the magnetic switch terminal on the starter. Put the gear shift selector in park or neutral, for vehicles with automatic transmission, or depress the clutch pedal and crank the engine and observe the voltage reading on the voltmeter. Also, check the voltage drop across the ignition switch and neutral start switch or clutch start switch, to know whether the readings are within the appropriate vehicle manufacturer’s specifications, and adjust or replace the defective switches as necessary. “Another possible cause of the starting system problems could be a defective starter relay, if equipped, so perform a continuity test with the relay de-energised and energised. If any of these tests do not match the vehicle manufacturer’s specified results, replace the starter relay.” Alternative voltage drop method Fatiha continued: “Checking the voltage drop across each component of the starting circuit is an alternative method to locate the cause of an excessive voltage drop. Leave the voltmeter positive lead connected to the positive battery terminal and move the voltmeter negative lead back through the circuit toward the battery. Continue to test each connection while cranking the engine until a noticeable decrease in voltage drop is detected. The cause of the excessive voltage drop will be located between that point and the preceding one.” Does the starter turn the engine too slowly? “The battery must be fully charged (12.6 Volts) and the battery cables, terminals and case in good, clean condition, including the frame and body ground connections and connections at the starter motor and magnetic switch. Excessive engine oil viscosity, particularly in cold conditions, will reduce the ability of the engine to rotate. This increase in engine drag will be transmitted to the starter during starter engagement, reducing its performance capability. Engine modifications can also change the operating characteristics of the engine and potentially introduce more force acting against the starter, which will mean it will need to be replaced.” Does the starter fail to crank the engine? If there is a high resistance somewhere in the starting control circuit, or the battery connections or cables are corroded or dirty, this will cause the starter to turn too slowly.” Does the starter rotate without rotating the engine? “If the starter is rotating but not the engine, check all teeth on the flywheel or flexplate ring gear to see if they are excessively worn, damaged or missing, by looking through the inspection plate on the bell housing or starter mounting port. A defective starter drive assembly could cause similar symptoms as a damaged flywheel or flexplate. If the starter pinion gear meshes properly, but does not rotate, it should be inspected for mechanical wear or damage.” Does the magnetic switch make operating noise when activated? “If clicking is heard when activating the starter control circuit and the starter does not rotate, the magnetic switch may not be receiving the voltage necessary to be fully activated. Check the starter control circuit for failed or damaged components and wiring, and loose, dirty or corroded connections. “If, however, the magnetic switch is receiving proper voltage, it may have burnt contacts. If the magnetic switch does not make any operating noise, it may be a defective pull-in coil or plunger.” Fatiha concluded: “For these, follow the vehicle manufacturer’s procedures and safety precautions to inspect the starter.” DENSO: STARTER TROUBLESHOOTING