Battery Voltage Low - most likely culprit?, Does not start well when warm Options

[Chaznaster]

Hi All.

I am having a trouble starting my carbureted 1.8 when the engine is up to temperature (heads at 310 degrees for over 30min). The engine is definitely turns over and the starter engages.

The car starts immediately when cool/ cold. It is also fine when I let it cool after being hot.

My battery seems to have settled out at about 12.2V. Per the Google, that equates to 60% useful charge. That is definitely a problem.

My theory on the non-hot start is that, as copper wire resistance increases with increasing temperature (also something learned on Google), it is just not getting enough current to the coil when hot. Cold wires = lower resistance = better current flow, and so, even with the marginal battery, it gets enough juice to start.

Now on to why the battery is running low. At warmed-up idle speed (800-900 RPM), the multimeter only reads 12.3. That is most certainly the cause of the low voltage.

I'd very much like your input as to whether this is likely caused by a voltage regulator problem or an alternator problem (or both).

EDIT: It will always start with a push start ...

Many thanks!

[fixer34]

Hi All.

I am having a trouble starting my carbureted 1.8 when the engine is up to temperature (heads at 310 degrees for over 30min). The engine is definitely turns over and the starter engages.

The car starts immediately when cool/ cold. It is also fine when I let it cool after being hot.

My battery seems to have settled out at about 12.2V. Per the Google, that equates to 60% useful charge. That is definitely a problem.

My theory on the non-hot start is that, as copper wire resistance increases with increasing temperature (also something learned on Google), it is just not getting enough current to the coil when hot. Cold wires = lower resistance = better current flow, and so, even with the marginal battery, it gets enough juice to start.

Now on to why the battery is running low. At warmed-up idle speed (800-900 RPM), the multimeter only reads 12.3. That is most certainly the cause of the low voltage.

I'd very much like your input as to whether this is likely caused by a voltage regulator problem or an alternator problem (or both).

EDIT: It will always start with a push start ...

Many thanks!

Alternator and/or voltage regulator are likely suspects since voltage at the battery should be in the 13.5v range while running.
BUT, does the alternator light in the combo gauge come on when you first turn on the key? If it does not, check/replace the bulb, then check the wiring. Silly as it sounds, the bulb must light up before starting/running the car for the alternator to work.