Starter Motor on Car Testing

Starter motor is that component of car as the name suggests which turns the engine of car On.
Starter motor usually have the following components in it but they may vary over the make of car and model :-
1 Armature
2 Field coils and pole shoes
3 Housing or Body
4 Brushes
5 Bushes
6 Starter Drive
There are 3 Type of Starters :-

• Inertia
• Pre-engage
• Gear reduction

In the Starter motor on car testing we require the following resources :-

• a suitable vehicle with a pre-engage starter motor
• a digital multimeter
• a clamp type ammeter with range up to 400 amps DC

The car on which i did the test was a Mazda 323 1989 model.
It was a manual transmission and there were no device on the car which required a power source for its memory. If there was any device which required a power source for its memory then we would have connected a 9 Volt battery in the cigarette lighter slot.

Then before carrying out starter circuit voltage drop tests we performed a Preliminary test in which we did the following steps :-

• De-activated the ignition or fuel injection system
• Checked the battery for serviceability
• Was the write range of meter selected or not
• Was the vehicle's transmission in neutral

Then we checked the Open Circuit Voltage across the terminal and it was found to be 12.4 v
if the voltage is 12.4 then % of charge is 50%
if voltage is 12.5v then % of charge is 75%
if voltage is 12.6v then % of charge is 95%
if voltage is 12.7v then % of charge is 100%
Open Circuit Voltage should fall between 12.4v and 12.6v.

Then we checked the available voltage across the battery terminal while cranking the cranking voltage spec is > 9.5 v and the cranking voltage achieved was 11.4v. If battery fails the cranking voltage test then the battery is rested so that it can gain some charge before continuing with this test.

Then we proceeded to check the starter circuit for voltage drop test.
In this test we needed a voltmeter and by using the voltmeter we checked the voltage drop across battery and the starter.
1 We checked the loss between battery positive post and solenoid starter input stud while cranking.
The spec for this test was 0.20v and i got 0.20v.
2 We checked the loss across solenoid main input and output terminal studs while cranking.
The spec for this was 0.1v and i got 0.1v.
3 We checked the loss between battery negative and starter motor body while cranking.
The spec for this was 0.2v and i got 0.1v

Then we added the total voltage drop across all the 3 and the spec for it was 0.5v and i got 0.4v.

Then we did the starter motor current draw test

In this test we require a Inductive ammeter (clamp meter)

The clamp meter set it at 400 amps DC and then push the Zero Button to zero the meter, if the reading doesnt Zero push the Hold Button and repeat the procedure.Once the meter is Zeroed pick up the meter and clamp around the positive battery lead anywhere between the positive terminal and the solenoid. Then with the help of someone the engine is cranked and then we get the reading on the clamp meter.
The starter should draw current between 125amps and 175amps but i got 96amps.
After all the test I conducted on the Battery i found that the battery was in good condition iit passed all the tests except the Starter motor current draw.