Starter Motor Testing

If your starter motor is refusing to turn your engine over, first check the battery has sufficient charge and is in god condition. Next, scrutinise the ends of both battery leads, plus the engine-to-chassis-to-body earth straps. The wires can end up making very poor contact where they’re crimped into the terminals. This can due be down to salt and moisture ingress or vibration. If they seem in good order, you’ve narrowed the fault down to the motor or solenoid. Test as shown in the diagram.

starter motor testing diagram
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2 Responses to “Starter Motor Testing”
  1. Andy Cole
    Andy Cole

    Really important to check the engine earth bonding strap as the alternative earth path could be via the choke or throttle cable and having 100s Amps passing through the petrol filled carb isn’t a good idea

  2. Roger Holman
    Roger Holman

    Long cable runs lead to voltage drop. Automotive battery cable is often composed of a relatively small number of heavy strands and is hard an un-manageable. If making new battery cables, use welding cable which is softer and more pliable, and has a much greater number of fine strands, giving it a greate cross sectional area and therefore less resistance. Use it for both pos. and neg. Try fitting an extra earth strap from a starter mounting bolt direct to the chassis, or the battery if it is close enough, anything to improve the current path can help an apparently tired starter.