How do fuel temperature and ambient temperature influence density and metering?

• A. Density decreases with temperature
• B. Density increases with temperature
• C. Temperature has no effect
• D. ECU uses density compensation to adjust fueling

Answer: (A)

Fuel density, like most liquids, falls as temperature rises. So when fuel gets hotter, the same volume contains less mass. That matters for metering because volume-based metering would deliver less fuel mass if no correction is made, throwing off the intended air–fuel ratio. Ambient temperature also changes air density: warmer air is less dense, so for the same intake volume, less air mass enters the engine, which would require less fuel to maintain the proper ratio. Modern ECUs compensate for these density changes to keep fueling aligned with the actual air mass entering the engine, effectively adjusting fueling to maintain the correct mixture.