[Vwdiesel] Glow plug comments

[Val Christian]

I don't know how difficult it is, but I'd just start with a continuity check 
on the GP.  Then, I'd give them juice, and make certain that the 
current "profile" is good.  What I mean by that is that they draw
a consistent current, as they heat up.  It might start at 14 amps, and
drop to 8 amps as the plug gets hot.  If one of them drops to 2 amps,
then it might be a problem.  This can happen when the conductive area
is erroded.  One localized area gets hot, (reducing current flow) and 
the overall temperature is lower.  This is analogous to an old incadescent
bulb, which runs at a overall cooler temperature (thus the "yellow" cast),
and dimmer.  Parts of the buld filament are running as hot as they should
but they are just the erroded parts.  The rest of the element is intact,
and due to the reduced current because of the "necking" of the filament,
it runs cooler.

The reason why I mention this is that while most of my experience is 
with IDI glow plugs, I have seen quite a few plugs where the 
continuity looks good, but the plug doesn't really get hot.  

Also, based upon my "quick read" of the 2003 glow plug system, the 
system does a "polling" of glow plug continuity.  According to mine,
#3 and #4 are broken or intermittent.  It might not be the plugs,
but I'll find that out next week, when I have time.  If it really
is the plugs, it is notable that I was able to start the car (parked
outside) in -4F (~-20C) weather earlier this week.  It wasn't pretty,
but it worked.

Also, on the old IDI glow plug issue.  There at least three "speeds"
of glow plugs out there.  The old (slow), the new (fast), and some 
which are even faster still.  In general, you can use the newer ones
with the old relay, but you'll get shorter life, with no real benefit.
You cannot use the older plugs with a newer relay, because they won't
get hot enough.  In a pinch, there is no problem using an older plug.
You can always "double cycle" a fast timer in cold WX.

Additionally, I always test a plug before installation.  Even a new one.
I've found bad ones that way.  Besides, I have a lot of old plugs 
hanging around, and it helps me assure myself that I've picked the
kind of plug I want.  For testing, I connect battery charger leads 
to the glow plug, and watch the current meter on the charger.  I also
watch the tip of the plug to see how hot it gets, and how fast.  
Observe the current drop on the meter as the plug gets warm.

If you're thinking of idiot lights for the glowplugs, the important
parameter is how much current the system draws at start up.  You could
do that with a ampmeter for the whole car, and get other utility out
of it.  I mentioned the hall effect device to measure current, it worked
great.  But if I did it again, I'd put it on the feed from the battery
to the electrical buss.  That way I could monitor charge/discharge.
That would work for monitoring glow plug starting current draw just
fine.  When you have a plug which is bad, you can trouble shoot and 
identify which one with other tools.  My regret was not putting the
hall effect device on the battery lead, and a second one on the 
altenator output.  Right now, I need to figure out how to fit a 
laptop into the 2003 Jetta, so that I can debug things on the fly
as the car gets older.

If you're going through plugs, the rule-out causes are: relay/timer or 
continuity to relay/timer sensor power/inputs; if the plugs look "cut"
injector patterns / drip; if the plugs look "cut" and your diesel
suffers from ingestion of pooled intake oil, that can be a problem
also.

I don't know the best way to get plugs these days.  The local parts place
tends to carry Champions, which I haven't had a problem with.  The
foreign parts places tend to carry Beck Arnley, which I have had problems
with, and Bosch, which are fine.  Years ago, the cheapest way to buy 
the plugs was by buying a replacement relay and 4 plugs (Hella) from
JC Whitney.  That way I got a small inventory of relays.  (They sometimes
collect water and fail.  They sometimes get hairlines in the solder
on the board (reflowing the solder fixes for a couple of years).  The
relay part of the relays tend to work fine.  The electronics for the timer
portion tend to fail.  When they do, you end up with short cycling,
and sporadic cycling, which are both problems.    Again, the TDI is 
different, and I don't have any real experience with it yet.

Val

> 
> Thank you, Val.  I'll give the glowplugs priority #1, then work back to 
> the relay.  Another poster also thought the glowplugs might be the 
> source.  I have the Bentley manual, but this is the first time any real 
> problem originated with the glowplug system so it remains to be seen how 
> well Bentley troubleshoots this beast. 
> 
> Tom K.
> ===================
> 
> Val Christian wrote:
> 
> >I have a similar problem on my 2003 Jetta.  I think mine is two 
> >failed GP.  I can let you know after mid-next week.
> >
> >Val
> >
> >
> >ps: I have the ebahn manual, but have not extensively read it.
> >
> >  
> >
> >>Vehicle:  1999 Jetta IV TDI, ALH engine, 62,150 miles
> >> 
> >> A few days ago the "check engine" light came on, and a query with the
> >> OBD-II reader got an error code of P0380, "Glow plug circuit."  After
> >> resetting the OBD-II, the light came on again returning the same error
> >> code.  A visual on the whole circuit from glow plugs to fusebox didn't
> >> find anything wrong, but after reading some of the responses in the
> >> newsgroup (I'm a newbie, BTW) the culprit seems more and more to be a glow
> >> plug relay (VW #038-911-253).  The "check engine" light comes on about one
> >> minute after starting, and starting is now (and always has been) darn hard
> >> for this particular car.  (My wife's 2003 Jetta TDI wagon starts
> >> immediately.)
> >> 
> >> Am I on the right track suspecting the glow plug relay?  
> >> 
> >> For the record, I replaced the timing belt, tensioner, idler pulley and
> >> anything else that moved in the timing belt area (except the water pump)
> >> last summer; no problems until now.
> >> 
> >> TIA,
> >> Tom Krummell
> >> Roseville, CA
> >>
> >>
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> >>
> >>    
> >>
> >
> >
> >  
> >
> 
>