S3 Diesel glow plug wiring

My latest project is now getting the usual examination and is proving difficult to start, I have noticed that the earth from the last of the glow plugs is not connected to the block although there is a lead there that isn't connected. Not being an expert I am not sure if this has been dealt with through earthing to the block via the plugs but I doubt it as the system looks very much how my other S3 is wired.

The plugs do not seem to heat with the ignition key in the right position so Im thinking of connecting the earth to the end of the series of plugs and see if that completes the series and therefore warms them.

Any views about the safety of this test, the following image shows the earth wire that seems to need to be connected.

https://picasaweb.google.com/lh/photo/Eq5gIV9Ov29WrfBaUwL-KjNVosnny_IE3ZibVdJRUfo?feat=directlink?

As no one else has come to your aid here I will try, those look like nice new red wires, how sure are you that your pre heaters are not the new parallel type?
If they are wired like the drawing (and it certainly looks this way) make sure you bypass the resistor wire on the baulkhead. leave the earth wire dangling, it is not required.

The plugs do not seem to heat with the ignition key in the right position

Click to expand...

Do you say that as you do not have a pre-heat light coming on?

Regards rog8811

take a glow plug out and have a look at it, if its got the curly end its original series connected type, meaning the interconnecting wires would not be in contact with each other, but if its plain rod then later parallel type this type earths through the plug wheras the series wired type needs an earth, i would guess from the wiring its later and if you connect up the earth to the main feed wear some dark glasses, if its the later type then they need 12v and so should not be fed through ther ballast resistor which drops the voltage to 7-8ish volts and makes starting harder

Also, if they're being fed off the ignition switch and they ARE parallel... wire in a separate push switch fed from a properly fused input to activate the plugs, as the current draw will soon eat the switch / wiring due to a higher load......

If they are parallel wired as dirtyrhino says they are quite easy to do. Did mine the other day as one of the previous owners idea of wiring was terrible and as stated they need a separate feed, switch and relay as the current draw is considerably higher than standard.
I used a new series3 petrol starter solenoid as my relay.