In an operating diesel engine, preignition...

🔍 Key Concepts

• Diesel combustion process – how air is compressed and how fuel normally ignites in a diesel engine • Difference between preignition (before intended start of combustion) and afterburn/overlong injection (continuing combustion) • Causes of hot spots or abnormal ignition sources in the combustion chamber

💭 Think About

• Think about what could cause the fuel-air mixture (or fuel spray) to start burning before the fuel is supposed to ignite from normal compression heat • Which option would most likely create hot particles or surfaces in the cylinder that could light off the charge early? • For each choice, ask: does this condition tend to delay, prevent, or advance the start of normal combustion?

✅ Before You Answer

• Be clear on the term preignition = ignition that occurs too early, not delayed ignition • Eliminate any options that mainly lead to poor combustion, misfiring, or delayed ignition rather than early ignition • Focus on the option that can create abnormally high local temperatures or combustible deposits in the air charge before the normal injection point

In an operating diesel engine, preignition can be caused by __________.

excessively late fuel injection

oil in the air charge

water in the fuel

injection continuing after the fuel charge is ignited

🔍 Key Concepts

💭 Think About

✅ Before You Answer