Thanks. This is a pin type glow plug engine. In many cases, even though the plugs continuity checks okay, they still are bad.

I would suggest that you replace all five glow plugs. In most cases this will make all the difference in the world. While you have them all out, check your harness by checking continuity between the disconnected plug at the relay to each of the eye terminals while disconnected from the plug. There should be continuity between each of the eye terminals and only one of the pins at the plug.

Good luck,