What causes a starter to crank slow?
In this regard, can a bad starter cause slow cranking?
A starter that's failing may crank the engine too slowly for a quick start, or it may not crank the engine at all. Often, the problem is not the starter but a low battery or a loose or corroded battery cable connection. If the battery's voltage is low and it doesn't take a charge, your customer needs a new battery.
Beside above, what is a slow crank? Slow crank: The starter cranks, but it does not produce enough engine RPMs to successfully start the vehicle. Click, no crank: The solenoid clicks, but the starter fails to crank at all.
Accordingly, what causes a starter to turn slow?
Slow cranking could be the result of several possible conditions, and as you've suggested, the fault might reappear or worsen. Possible causes are a degraded or defective battery, faulty electrical connection, a charging system problem, a bad starter or battery rundown when parked.
What happens when the starter motor starts under load?
During starting of this motor under load, the high initial current, due to low resistance and no back emf, produces a very strong magnetic field and consequently high initial torque. This characteristic allows the series wound motor to be an ideal starter motor.