During main engine performance testing it is noticed that the firing pressure of one cylinder is higher than the average, but cylinder compression pressure is normal. Which of the following would most likely be the cause?

Correct Answer: Option A — Early fuel injection

Early fuel injection introduces fuel before optimal top dead center, prolonging ignition delay and causing an excessively rapid pressure rise that spikes peak firing pressure while leaving compression pressure unaffected. Marine diesel operators diagnose this via indicator cards showing sharp, premature pressure peaks.