85 Turbo Hard starting - Input shaft seal or glow plugs?

[gamber]

I have a 85 Jetta Turbo Diesel.  It has developed a hard starting issue when cold, specifically when sitting for a longer period of time.

Problem
- car bucks and is VERY difficult starting
- smoke is black
- smoke under the hood when starting
- evidence of very slight fuel around the pump.  Not worse or better than the past, just the same

Unusual
- car starts very well when plugged in - even if it is 4 hours or so

Suspected the glow plugs, here is what has been done:
- troubleshot the electrical
- power to glow plugs, do not have the tools to measure how much amps they are pulling

What is next?
- suspect that the pump is losing its prime
- have read about the input shaft seal, what type of project is it to replace the seal without removing the pump?

Please offer your suggestions on how to troubleshoot and solve this problem!

[jtanguay]

if the pump was losing prime, it would start like crap even when plugged in.

my money is on the glow plugs, and or battery if its not cranking fast enough.

i suggest spraying the pump with compressed air around wet spots you may suspect.  then keep an eye on them.  if your pump is losing internal pressure, that could very well affect starting.

[Smokey Eddy]

bucking when starting (or trying to start) i found to be a timing issue.
try advancing and retarding the timing and seeing if that makes any difference? be careful not to torture the battery too much though.

[gamber]

Smokey Eddy,
Thanks for the input.
Question is how would the timing be suddenly out of wack?  Would that not apply both when hot and cold?  How can I trouble shoot?

Thanks

[Rabbit TD]

Smokey Eddy,
Thanks for the input.
Question is how would the timing be suddenly out of wack?  Would that not apply both when hot and cold?  How can I trouble shoot?

Thanks

I'm betting it's the glow plugs too if it starts fine when you plug it in.  I see you live in Canada too and i amazes me that you all can get these things started at all up there and it has been colder than usual lately. The smoke under the hood is probably coming between the doghnut gasket on the downpipe due to the shaking.  The timing probably isn't off or by much if it does start when it's plugged in. The only way to know it if is right though is to use the dial indicator.  I would just go ahead and pull all 4 plugs and test them individualy to see if they get red hot and eliminate all the guesswork about resistance testing them and then half the battle is done, they're already out to replace with good ones, I'd put all 4 in if I were you and keep the ones you have now that test good for spares.  All my Rabbit diesels I've ever had always started on 3 cylinders for just a little and then catch on when it gets below about 25F down here and they were all good compression clean fuelsystem and ran as good as you would ever want.  I don't know how these later diesels are but the old ones like you're talking about all act like that especialy with glow plugs that aren't up to snuff.  Maby think about going to a little thinner oil too for your temperatures till it gets warm again.