[Vwdiesel] 98 TDI no glow

Tad tadc at europa.com
Fri May 22 13:28:09 PDT 2009

What is the ambient temp when this happens?  Unless it's pretty damn cold
there (lets say, below freezing), you shouldn't need glow plugs to start a
properly timed engine.

Also, a real-short GP light (again, assuming above-freezing temps and
low-ish altitude) is totally normal.

Which makes me wonder if the timing is indeed set properly.  Did you do it
with VagCom in basic setttings mode?  Is it set to the advanced half of the

If it really is set right, we get into the realm of the less likely - pump
advance problems, injector pressure/pattern problems, starter/battery
related problems.  Actually come to think of it, starter/battery (slow crank
speed) is probably the 2nd most likely scenario.  At least it is on the ALH
models - I'm not as familiar with AHU but I think the same principles apply.
If the engine wont start AT ALL, assuming you're not in the arctic or
something... it sounds like something else is definitely wrong aside from
the GPs - which *sound like* they are working correctly.  Even with no glow
at all, a DI diesel should start (perhaps with some difficulty) unless it's
RealDamnCold and/or you're in the mountains or something.
Which is a long way of saying - I think you're barking up the wrong tree
with the GPs.  You've proven they work (when you pull the temp sensor).
You've changed the temp sensor (so it's probably not bad), so it's very
likely that the GPs are functioning as designed.  Time to look into another

Good luck with the car!


On Fri, May 22, 2009 at 10:50 AM, jonathan hoehl <jjhoehl at hotmail.com>wrote:

> I need some help.
> Same tdi that wouldn't start a few months ago.  Timing cog changed and
> timing perfectly set.  Engine runs great!  But, no glow cycle.  When you
> turn the key, the glow plug light comes-on for a second then turns right
> off.  It acts like the engine is already hot, when it's not.  The
> temperature gauge reads as it should too.  If I disconnect the 4-pin coolant
> temp sensor that's right next to the head, the temperature gauge doesn't
> work, the computer seems to think the engine is always cold (adjusts timing
> accordingly), and the glow plugs stay-on for quite a while (20 seconds
> maybe?!, seems kinda long).  This is an AHU engine and I got the car with a
> black 4-pin coolant temp sensor with a yellow paint dot on it.  I bought a
> new black 4-pin coolant temp sensor from the dealer with a blue plastic ring
> around it.  They said this blue one is the correct replacement.  Both temp
> sensors make the car act in the same fashion.  Basically the car runs fine
> and everything works correctly when the engine is WARM and with either
> (yellow or blue) coolant temp sensor plugged-in.  Seemingly because I don't
> need the glow plugs to start the car when the engine is already warm.  The
> problem is a cold start, the glow plugs won't cycle and the engine won't
> start without them - unless I unplug the temp sensor and the glow plugs
> cycle 'as they should'.
> Does anyone have a thought about what could be wrong?  And, is anyone using
> a different temp sensor for this engine?  I can't remember if this is
> related, but the brake lights are ok.
> Jon
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