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!

[rhodyguy]

Starts fine when cold? When it’s hot it still spins up, just won’t catch? Have you considered hot fuel? When you are starting when hot, are you touching the gas pedal? My car (Webers) stumbles at startup when hot. 3 pedal pumps then feathering the pedal. You have to get those throttle plates open. Things calm down when the carbs are full of fresh tank fuel. Actually it’s only a few seconds. Are you using phenolic spacers/gaskets on the intake bases? I thought the voltage numbers were more about what the ‘brain’ needed to function.

[Chaznaster]

Starts fine when cold? When it’s hot it still spins up, just won’t catch? Have you considered hot fuel? When you are starting when hot, are you touching the gas pedal? My car (Webers) stumbles at startup when hot. 3 pedal pumps then feathering the pedal. You have to get those throttle plates open. Things calm down when the carbs are full of fresh tank fuel. Actually it’s only a few seconds. Are you using phenolic spacers/gaskets on the intake bases? I thought the voltage numbers were more about what the ‘brain’ needed to function.

It starts great cold and most of the time hot. I have a single, central Weber 32/36. It is not over the heads so should not get excessively hot. I am running the spacers, as well, just in case. I usually give it a single pump on the throttle to reset to fast idle. When it does start it comes right to life.