Hi,
It is possible to test all the glow plugs at the same time without disconnecting, but you require a current probe, the one that has openning jaws, and a DVM.
I have just checked mine and from cold they take 80/90Amps, dropping to about 50/60Amps at the end of ther timed period.
The jaws of the probe that I have are too fat to allow a test between the plugs.
Regarding the 8mm nuts, I use manetic tip from a screw driver, holding the tip on the middle of the nut with one hand and rotating the nut with the other, untill the nut bites on the thread.
Duff glow plugs??
Moderator: RichardW