If there is no timing mark on the crank pulley, you can determine where TDC is by pulling out a spark plug and rotating the engine by hand to see where the spark plug gets to the top. If you have put a screwdriver down the hole and use that to move a dial gauge, that will get it to within a degree or so. If you can’t, or you don’t have a dial gauge then you can screw a bolt into the spark plug hole and roate the engine until the piston touches the bolt near TDC, and mark that position on the crank. Then rotate the engine back the other way until it touches the bolt from the other side, and mark that position. TDC is halfway between those two marks.
This assumes that you have a running engine that will idle by itself.
You will need a timing light; the dumber and more basic the better. If you’re using a timing like that has intelligence in it and advances or retards the time of the flash relative to the ignition trigger, then you must disable that.
On COP engines, there’s no ignition lead so you can’t clip the pickup on the lead. In most cases you can clip the pickup on the leads at the back of the ignition coil, because the common mode current is the same as the high voltage current by Kirchoff’s current law. I have never seen this not work, but if it fails you can remove the coil and connect an ignition lead between the coil and the plug. On some Nissans, they have a timing loop which you are supposed to be able to clip your timing light onto, but in my experience this often doesn’t read correctly so I recommend against using that.
Timing light clipped onto the back of the COP
Then check the timing with the timing light, and adjust the ignition timing using the up and down arrows to change the base trigger angle until the timing light shows the same number commanded by the ECU. You should also increase the revs and make sure that the timing stays still.
Thank you and happy learning!