Push Rod Method
This method is like the spring method and you check that the push rods are free to turn. The unit at TDC will have loose springs. The care that must be taken is that it should be used along with the flywheel method and should be used in a working engine. By a working engine, I mean the engine that was running and has been stopped for tappets adjustment.
Spill Timing Method
This is a very accurate method generally used to check the start of injection in the fuel pump. It will also give you the injection TDC. It is used not in the tappet checking process, but instead to find the start of injection when you have power or thermal balance problems.
Basically in this method the delivery valve of the fuel pump along with the delivery valve spring are removed. There after a special “U” shaped pipe is put in place of the high pressure pipe. After this operation the engine is turned by the turning gear and slowly brought near the expected TDC.
Soon oil will start spilling out of the pipe because the oil is entering from the inlet port, which is uncovered by the plunger. Keep turning the engine slowly and the oil quantity will reduce. The point where the oil flow just stops is the start of the injection. At this moment the plunger of the fuel pump has closed the inlet port and if you observe the fuel cam, you will find the follower is no longer at the base circle.
As this method involves the spilling of fuel, it is called the spill timing method.
