Glow plug warm up times

[to3m]

As it's getting cold my 330d (2001 model, 185hp) is starting to need longer for the glow plugs to do their thing when I start it after it's been left. I don't know exactly how long it takes, because I haven't timed it, and it always feels like an absolute age when you're just sitting there watching the light, but it might be about 4-5 seconds. After that, the engine starts without any reluctance, and then runs about as smoothly as you'd expect, so it doesn't seem like there's anything obviously wrong.

But the warmup step never took this long with my 320d (2001 model, 150hp), not even after it spent 2 weeks under a snow drift last winter...

Is this normal (bigger engine, non-TU version, etc.), or should I get ready to start spending?

[TheEnd]

http://wds.spaghetticoder.org/en/zinfo/FIN0898FB57...

At least 4 secs, longer if colder.

[to3m]

TheEnd said:

http://wds.spaghetticoder.org/en/zinfo/FIN0898FB57...

At least 4 secs, longer if colder.

Ah, nice. Thanks!

(From poking around that site it seems like M47TU engines have DDE 5.0, with much shorter preheating times - http://wds.spaghetticoder.org/en/zinfo/FIN0201FB47... So that explains why my old car was much quicker.)

[hman]

I never even look for the light, just switch it on and start up - no problem...

[anonymous-user]

Early cars used 12v glow plugs, which on cold days with a lower battery voltage, take longer to heat as the starting temperature falls. Later cars use 5v glow plugs and pulse width modulate the heating power to achieve consistent plug heating across a much wider range of temperatures and battery voltages. Also, because they can control the heat output, they can be switched on initally at a very high power setting (using all 12V into a 5v plug), this heats the system very fast, and then the contoller reduces the voltage to prevent damage to the plugs.