Diesel Engines Cold-Starting

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Diesels can be hard to start in cold weather if the glow-plugs are not in good condition To check them, take out each glow plug*, connect a wire to the top screw terminal and place across a 12v source; watch the carbon rod, if it glows red then the glow plug is in fine fettle. Inspect the carbon for burning and missing pieces - once satisfied it is in good condition replace in engine or if not get a new one. Torque to no more than 16 Ft-lb (22 Nm), but first check that the sealing sleeve at bottom of thread has bot been crushed by previous over-tightening - the ring gap should not be closed up, should be approx. .5mm (20 thou). If not replace glo plug.

NB. It is rarely worth removing glow plugs and not replacing with new ones, as they are not the easiest things to get at.

  • A special (Magnetic) ratchet spanner is used to remove these on VW diesels, available from Snap-On or Blue-point tool vans (about £15) Some say it is a waste of space :) Might be handy to nip up the bubar nuts

Tip by Ringo: Keep the two difficult glowplugs (under the pump) attached to the busbar, by just loosening the busbar nuts slightly. This helps removal and then likewise pre-attach the new two front glowplugs to the busbar which helps positioning them.

NB: Importnat, do not vross-thread the plugs, make sure they have started straight before spannering!

Once you have been through the four plugs and you are happy they are working then check the bus-bar that connects the four plugs together, make sure you have a good electrical connection between the bar and the plug, connect a multimeter, pos to the bar and neg to an earth source, turn on the ignition when the motor is cold, it should register 12v+ for the time the relay is set for or until the lamp exstinguishes on the dashboard, any failure here is either the relay or if its fitted an over zealous temperature sensor which is not allowing the plugs to go live

Hope this is of some help.

NB. Don't forget to check the fuseable link is intact (in the eletrics box under the relay)

HarryMann: About 55 amp fusible link for the 1.6TD, GSF normally have them for a few pence, worth carrying a spare!

Simon Baxter: White Smoke. White smoke is cool combustion temperatures.

They also seem to do this when the head has been off or the pump is tired, they don't like starting without the cold start handle pulled out.

Could be absolutely allsorts, headgasket, pump timing, tappets, low compression, loads of stuff.

Start at the beginning, compressions, set bucket and shims, set cam timing, set pump timing and work through it methodically