Battery Voltage¶
The electrical system's voltage. It sags while cranking, and a weak battery slows the starter, weakens the spark and starves the fuel pump.
What it is¶
The system voltage is shown as the VOLTAGE bar in the left readouts. Typical values:
| Situation | Voltage |
|---|---|
| At rest | about 12.5 V |
| Ignition on | about 12.2 V |
| Cranking | 9.5–11 V |
| Running | about 14.2 V — the alternator cuts in at about 1000 RPM, is full by about 2500 RPM, and delivers up to 100 A |
Why it matters¶
Voltage reaches into several systems:
- Starter torque scales with voltage — cranking slows as it sags.
- Fuel pump efficiency falls below about 14 V and the pump stops below about 8 V (see Fuel Pressure).
- Injector dead time rises with falling voltage (× 14 V ÷ V, up to 2×) — see Injectors.
- Spark energy falls, so the engine is weaker to catch (see Starting an Engine).
- Below 8 V the ECU fails.
Long or repeated cranking drains the battery, and the cooling fans draw 10 A.
How to tune it¶
Voltage is an input you watch, not a setting. If cranking sounds slow or the engine is weak to catch,
check VOLTAGE before touching the enrichment curves. Cranking with low voltage, and cranking too many
times, also wears the starter (see Damage & Wear).
Rule of thumb
Weak spark and a slow starter on a cold morning are a voltage story as much as a fuel one. Watch
VOLTAGE while you crank.
In the game¶
Warning light 3 (battery / electrical) comes on under 10 V or if the starter is worn (see Warning Lights & Engine State).