MEO FUNCTION IV

How to know which unit piston is at TDC?

Fuel Pump Method

The most accurate method to know the position of the piston without opening up the piston is the fuel pump window. The fuel pumps have a window and as the plunger goes up and down, so does the mark on the bottom spring holder. On the body of the fuel pump there are cut marks which show the start of injection. In a diesel engine the start of injection is the injection TDC where both the inlet and the exhaust valves are closed. In this injection TDC we can check the tappet clearance. It must be noted however that the injection TDC is not the absolute TDC as the piston is still some way down depending on the design of the engine. An injection TDC may be around 5 degrees before TDC.

About the author

Anand Gautam

Anand Gautam is a marine engineer, Graduated from M.E.R.I. Mumbai. He likes to sail onboard ship and is one who is passionate about his job. He loves to share his knowledge, information, and ideas to everyone in a simplified way just for his satisfaction.

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