During main engine performance testing it is...

Question 1 of 270705eccefa3bacbc34ba4d47e0c

During main engine performance testing it is noticed that the firing pressure in one cylinder is lower than the average, but cylinder compression pressure and fuel pump delivery rate are normal. Which of the following would most likely be the cause?

Back

Question 1 of 27070

🔍 Key Concepts

• Difference between compression pressure (air only) and firing pressure (after combustion) • How fuel injection timing (early vs late) changes peak cylinder pressure and temperature • Whether engine load or piston ring condition would affect one cylinder only, given that compression and fuel delivery are normal

💭 Think About

• If compression pressure is normal, what does that suggest about the condition of the piston, piston rings, and valves? • How would late injection versus early injection change the point in the cycle where maximum pressure occurs, and what would that do to the measured firing pressure? • Would a change in overall engine load explain a low firing pressure in only a single cylinder, or would you expect to see similar readings in all cylinders?

✅ Before You Answer

• Confirm that normal compression pressure generally rules out major air‑side leakage like badly worn rings or valves for that cylinder • Consider whether fuel pump delivery rate being normal means the quantity of fuel is okay, leaving timing as the suspect variable • Check which option specifically affects combustion timing in one cylinder without changing its compression pressure or fuel quantity