Technical Crack but not fire, now fixed, but motor slow turn over

[43576]

Two weeks ago, I had an issue starting my car, a Panda 1.2. It was a cold morning, around 13°C, and before heading to work, I found that it would crank but not fire up. I tried three times then the engine started. Over three consecutive days same problem.
I bought new spark plugs, but the problem persisted.

Upon further investigation, I discovered that the negative wire from the battery to the body was covered in corrosion green mould. I replaced the wiring and the battery clamps.

Now, the car starts on the first attempt without delay. However, I've noticed that the starter motor doesn't turn quickly for the first two seconds before firing up.

Could this indicate a faulty motor? I tested the battery before starting; it read 12.5 volts but dropped to 9 volts while starting. The alternator generates electricity back up to 14.2 volts once the engine is running. After turning off the engine, the power slowly decreases from 13.2 volts to 12.6 volts.

Is this normal? I don't think there is anything wrong with the alternator.

 

[koalar]

Measure the voltage

From a clean bit of cylinder head

To a cleaned up top of the battery negative terminal

While cranking

Post results

 

[DaveMcT]

Put a jump lead between battery negative and bare metal on engine. It the the starter speed improves, it show you still have a dirty earth connection.

However your voltage information suggests the battery might be weak. A good one should be well above 9V after three start attempts.

The 100HP or diesel spec Yuasa will last for ages in a 1100/1200 and the cost is not so much more than a smaller battery.