ICE-39 — Cold Start

ASSUMPTION — This lesson covers cold start conceptually; specific temperature thresholds are not given.

In this lesson you will learn:

• Why cold start is hard
• Enrichment and catalyst warm-up
• The diesel glow plug

1. Why Is It Hard?

When cold, fuel vaporizes poorly, oil is viscous (high friction), and the catalyst is not yet active. These three factors make starting and emission control difficult.

FACT — Unvaporized fuel does not ignite, so a temporarily richer mixture is needed; cold viscous oil also raises the cranking load.

2. Enrichment and Catalyst Warm-up

FACT — The ECU uses a richer mixture at cold start, returning to stoichiometry as the engine warms. It also adjusts ignition/intake strategy to reach catalyst “light-off” quickly, since a cold catalyst controls emissions poorly (ICE-22).

3. Diesel Glow Plug

FACT — In diesels, compression heat may be insufficient when cold. A glow plug pre-heats the chamber to ease ignition; the ECU manages glow duration by temperature.

4. Summary

• Cold brings vaporization, viscosity and catalyst-efficiency problems.
• Temporary enrichment is used.
• The catalyst must warm quickly.
• Diesels use glow plugs.

5. Sources

• Bosch, Gasoline-Engine Management and Diesel-Engine Management

Next Lesson

• ICE-40 — Engine Calibration.