[Vwdiesel] Burned out glow plugs [Hot balls]

[Sandy Cameron]

At 08:31 AM 22/09/04 -0500, you wrote:

 Puzzled now, I pulled the 
>first glow plug and found a small piece missing from the plug.  Not at 
>the end, like I am used to seeing when you have a leaky injector, but 
>about 1/8-1/4" back from the tip.  Checked it with the battery charger 
>and sure enough, no glow.  Now I decided I must bite the bullet and 
>pull all of the plugs, a hard chore made harder by the "spaceship" on 
>the turbo pump.  Anyway, all plugs out, all plugs dead!  One other 
>plug, had a small piece missing also but the other two looked OK 
>visually but all tested no glow with the battery tester.  Luckily I had 
>some used plugs from the Ecodiesel engine that I bought so I just 
>swapped those in and vrooom, car starts right up.  When my son got here 
>last night, we hooked a volt meter to the glow plug bar and timed the 
>glow plug relay - 7-9 seconds with power to the glow plugs, then relay 
>clicks and no power to plugs.  So here is my problem, the plugs were 
>new when I put the engine together so they have ONLY 10000 miles on 
>them.  What gives?  I didn't check to see if power came back to the 
>plugs after start up, but I can't imagine the relay closing again after 
>the key is in the run position.  Any input would be appreciated.  I am 
>down to only 3 fast plugs in my possession so I can't replace them all 
>again without an outlay of money and I would rather not do that.  BTW 
>they were Bosch glow plugs, I don't buy anything else.  hayden

I would agree with Val that injectors are leaking on the ones that have
holes in them. Do the holes look "eroded"? (burned away)

But that would not account for the other 2. Time to install a "Tattle-light"
direct from the buss, that is visible to the driver. inside the cab, or at
the back of the hood where visible to the driver. Make it noticeable enough
it can't be missed when on.

Theorizing:
If the glow plugs come on while motoring with an up-to-temp engine, and esp,
at speed or under load (lots of coal being shovelled), the combimnation of
high voltage (13.6v) provided by the alternator, and external heat provided
by the cheerfull roaring fire in the pre-combustion chamber, could heat them
to the fail point.
The "erosion" could be caused by a normaly harmless abberation in spray
pattern, that under the circumstances, with the plugs heated from within,
was just too much for the outer jackets to take.

Hot Balls!

Most pre-combustion chamber type diesels have a "hot ball" in the chamber
(EG, Mercedes) that keeps the fire going reliably after the engine starts.
Mercedes' is an actual little ball on a rod that's right in the spray from
the nozzle, it's glow plug is a separate hairpin loop of wire that catches
the edge of the spray for starting. (I'm talking about the two old ones I
had, they may have gone to the less intricate VW method by now.)
 In the VW, the tip of the plug is the "hot ball".
When the engine is up to temp, the tip of the plug is kept at a red heat
with the power off, to ignite each injection reliably. If this heat from the
burning fuel is combined with the heat from the internal electric element,
your balls will become too hot, and probably melt.

Install the Tattle-light.

Sandy