[Vwdiesel] glow plugs

[Shawn Wright]

> Is it common for all four glow plugs to fail at about the same time? If 
> one or more glow plugs are shot, do the remaining plugs each get more 
> current because they are connected in a paralel circuit?

No, the current should remain roughly the same per plug regardless of # of plugs 
working.

 If this is the 
> case, does the failure of one quickly cause the failure of the rest from 
> over current (overheating)? 

I don't think so.

> Can cycling the glow plugs on especially cold days cause them to fry 
> faster?

I suppose, but I doubt it. 

> Normally, I go to the block heater when the overnight temperature goes 
> below 10 F. Last night, my daughter forgot to plug hers in and the temp 
> went to 4 F this morning. No Start! I got it running this afternoon but 
> later on it would not start again when the temp had improved to around 
> 20F. I jumped it and had plenty of cranking but not even a wimper of 
> firing. When I finally got it home around 8 this evening, I checked the 
> fuse (only a 10 A on an 85 Golf?) and it was fine. I pulled the glow 
> plug from #4 because it is the only easy one to get out and found it 
> failed the ohm meter test for continuity. I'm sure the other three are 
> the same way. I just had all of these  glow plugs out at the end of the 
> Summer and they were all good.
> What would cause all the plugs to fail so quickly?

I just experienced roughly the same thing - 3 of 4 were dead 2 weeks ago after they 
all checked out fine in the summer. Don't assume all of yours are dead though. At 
20F, I'd expect it would start on 3 plugs, but just barely start on 2. Mine took a *lot* of 
cranking to start on 1 plug, and the temp was about 5C (40F). 
I still don't know why 3 of mine failed, and then two more failed a week later. The first 
could be just age, and the second two were also used plugs, so who knows? 
However, I do find it a bit suspicious that the two plugs that failed in a week were also 
in the two cylinders with low compression and valves way out of adjustment. 
Have you done a compression test or checked the valve adjustment lately?

If you're planning to pull all the plugs, I recommend pulling the fuel lines off - makes 
the job a lot easier. I used to disconnect the bus bar from #4, 3 and 1 then test 
continuity on 1,3,4 directly using a gauge, and using the busbar for #2. I find #2 the 
hardest to reach, so I would only remove the nut if I had to. Now, I have each plug 
wired separately to #4, so I can detach & check easily. The wires also allow you to 
loosen the nut, then remove the plug & re-install using the wire as a holder. (no more 
dropped nuts). I used parts of the bus bar crimped to 10ga wire, but eyelet rings 
would also work well. 10 or 12 ga wire is sufficient for the current of one plug.

--
Shawn Wright
I.T. Manager
Shawnigan Lake School