So my 2005 CRD has been taking a few seconds longer to crank over on a morning now that the night time temperatures are getting a little lower here in Scotland. Nothing really bad but 3 or 4 seconds cranking before starting with a puff of grey smoke so I decided id change the glow plugs. Removed the alternator and took the first plug out to check what it had fitted before ordering new ones and found that it looks like the previous owner replaced them pretty recently (I bought it 3 weeks ago) but has used NGK 11v plugs instead of the 5v or 7v ones I was expecting to see.

I tested it with a 5v supply and it got hot but didn't glow, unfortunately I don't have a 7 v supply. 12 volts across it had it glowing red as I expected so would I be correct in thinking this is the cause of the slower starting as the plugs wont get up to temperature when only being supplied with 7v?