The basic steps of starting system troubleshooting should be followed here and as always start with the following.
- Verify the Complaint T he two most common problems you will hear about with a starting system are no cranking and slow cranking. To some operators, not starting means not cranking, and in any case, where there’s a starting complaint, you need to see for yourself what is happening. If the problem is happening now, then get the operator to show you. If the problem is intermittent, then ask when and under what conditions the problem is occurring. You can try to recreate it or you may have to return at another time.
Always check to see if the problem isn’t simply part of the starting interlock system or that there is extra resistance to cranking the engine being caused by other factors (wrong engine oil viscosity, hydraulic system load, drivetrain load).
Once you have verified there is a starting system troubleshooting problem, then you can move on to diagnose it.
- Check the Simple Stuff First T here are many checks you can make before getting any tools out. A good HDET sensory check (look, listen, smell, feel) may detect the problem. Visually look for loose or corroded cable and wire connections, battery defects (cracked case, missing vent cap, dirty top, loose/broken/missing hold down), loose starter mounting fasteners, loose switches or relays, and loose or broken control switches. With electrical systems your nose may tell you that the starter has been overheated or some wiring has melted. Carefully feel for hot wires and components. Air and hydraulic systems should be carefully checked for leaks. Never use your bare hands to check for air or hydraulic leaks. Use a piece of cardboard or wood. Check to see if there are other electrical system problems by turning on lights, wipers, or fans.
- Check the Battery Systems T he battery condition and charge state should always be confirmed when looking into any starting problem. After a thorough visual inspection (checking electrolyte level if possible), check open circuit voltage (OCV) of the battery systems. This should be a minimum of 12.4V for a 12V system and 24.8 for a 24V system.
Once a good battery condition has been confirmed and a visual inspection of the rest of the system hasn’t uncovered any defects, then you can move on to determining whether the problem is in the starter control circuit or the main power circuit. This will be done with available voltage checks.
- Checking voltage at the starter solenoid is a good place to start. Have an assistant try to start the engine while you are checking for voltage at the S terminal on the starter solenoid. If there is battery voltage at the S terminal, then you need to focus on the starter assembly and battery cables. If there is less than battery voltage, you will need to focus on the starter control circuit.
Once you have decided which part of the system is defective, you should be checking for available voltage and good ground through the system. Voltage should be very close to battery voltage, but if you find voltage and it is less than it should be, then you should start performing voltage drop testing throughout the control circuit. This will be done with the circuit energized. You are looking for excessive voltage loss that will indicate high resistance. The likely places for this are connection points such as wiring harness connectors and switch or relay terminal.
The control side is all about sending power to the S terminal but relays will need a good ground to operate. Some likely problems in the control side are the following:
■ Faulty key switch
■ Faulty interlock switches/sensors
■ Faulty relay(s)
■ Loose, corroded, broken, or dirty wires
■ Open circuit protection device