28-04-2023, 07:35 PM
Hi Denis
Regarding the starter motor, two possibilities spring to mind. If there is excess electrical resistance anywhere in the starter circuit, including the motor itself, the current will be smaller than it should be and the torque will be much reduced (torque depends on the square of the current). When I say excess, even milliohms will have an effect.
On the other hand, if there is excess mechanical resistance, the starter motor will struggle to get up speed and the current will climb right up towards its stall value, I don't have an exact figure but let's say 300 amps.
I suggest you check the battery voltage drop whilst the starter is turning. I'd expect it to drop to maybe 4 volts under stall conditions or 5 volts under normal conditions. A smaller drop would suggest the current isn't enough. If you haven't got a voltmeter, even the brightness of a sidelight bulb across the battery might give you some idea. The ideal would be a clamp on ammeter so you can measure the actual consumption.
In the past, I have encountered high starter motor resistance due to a dirty commutator, weak brush springs, sticking brushes and corrosion hidden under rivet heads. The switch on top of the starter is another possibility, shouldn't be too difficult to bypass and/or take off to inspect.
I remain optimistic that the noise is coming from the starter motor due to some sort of fault !
Regarding the starter motor, two possibilities spring to mind. If there is excess electrical resistance anywhere in the starter circuit, including the motor itself, the current will be smaller than it should be and the torque will be much reduced (torque depends on the square of the current). When I say excess, even milliohms will have an effect.
On the other hand, if there is excess mechanical resistance, the starter motor will struggle to get up speed and the current will climb right up towards its stall value, I don't have an exact figure but let's say 300 amps.
I suggest you check the battery voltage drop whilst the starter is turning. I'd expect it to drop to maybe 4 volts under stall conditions or 5 volts under normal conditions. A smaller drop would suggest the current isn't enough. If you haven't got a voltmeter, even the brightness of a sidelight bulb across the battery might give you some idea. The ideal would be a clamp on ammeter so you can measure the actual consumption.
In the past, I have encountered high starter motor resistance due to a dirty commutator, weak brush springs, sticking brushes and corrosion hidden under rivet heads. The switch on top of the starter is another possibility, shouldn't be too difficult to bypass and/or take off to inspect.
I remain optimistic that the noise is coming from the starter motor due to some sort of fault !