Cranks but no start on low battery 1996 Eldorado

[ToxicDepression]

My battery reads about 9.8V after sitting for a day or so, it turns over, but am curious if the coils require a certain amount of electricity to start the spark plugs. Or do I just need a new battery. It will start with a charger/jumpercables, alternator is fine. Battery just wont hold 12+ volts for long, paracidic drain might be the answer, but so far I wont diagnose that yet. There are no codes that are active.

[rockfangd]

Have the battery tested but likely it is bad.

Also very important to ensure your connections are good and tight.

Also note that a bad battery or low voltage problem will take a toll on the starter and alternator. It tends to be very hard on them

[Göran W]

Disconnect after drive and check voltage immediately and after a few hours. Below 12 volt - change battery!

[Cadillac Jim]

If the battery drops below 9 Volts during cranking, the modules may not work properly until the voltage comes back up. This will also throw codes that tell that the low voltage event happened. The car should still start if the battery does not go much lower than 9 Volts. But if the voltage drops still farther, some modules may cut out completely, including dropping stored codes. To start the car, you need the PCM and ICM to have ignition, and probably others. If the battery is at 9.8 Volts before you turn the key to start the car, it's likely that you are going down to 8 Volts or lower.

I would keep the car on a trickle charger or battery maintainer until I got the battery checked. As rockfanged says, the battery is very likely bad. Göran W has a good way to make sure that the problem is not someth8ing in the car killing a good battery.