I used a snap on gauge that reads up to 500 psi. It connects to a fitting that screws into your glow plug port.

You have to remove all 8 glow plugs. Then screw the fitting into one glow plug hole at a time. Be sure to put some anti sieze on the fitting that screws into the glow plug hole.

It is hard to reach all the glow plug holes becaue the injector lines are in the way. You may have to loose the injector lines as necessary.

Crank until the pressure stabilizes. My gauge held the pressure so I could look at it after cranking.

Mainly you are looking to see if one cylinder might be much different than the others.