1985 mk2 jetta crank, black smoke, no start

[PENNY RACER]

My name is Jeff. My son Dillon and his best friend Josh just bought a 1985 Jetta diesel. It had no battery or starter. Josh bought a starter and battery. After double checking the timing belt install and setting the pump timing, it still takes a loooong time to start.
I have bled the fuel lines and have good fuel at the injectors. I have bypassed the glow plug circuit and went straight to the battery, It cranks a really long time before it starts. Makes a LOT of black smoke when cranking. Once it is running, it takes throttle to keep it running, it let the pump lever go back to idle, it will stall. Then it takes an act of congress to get it running again. It seems to run ok and does not make any unusual noises. But I have to hold the throttle about 1/3 way open to keep it running. revs up fine once it is running. Any advice would be greatly appreciated.

[ORCoaster]

If this is a newly purchased car and it cranks hard then I would be checking those old glow plugs.  They are not a forever item and when they go it "takes and act of Congress" to get the engine to start.  By the way that statement has taken on a new meaning over the last couple of Congresses.  Do they even know how to pass an act anymore.

The black smoke is over fueled exhaust so my guess is not prewarming the cylinders before injecting fuel.

The idle screw may need to be set on the pump to get it to do its job of holding an idle.  Someone may have messed with the fuel screw as well thinking that was the way to control the idle and all that does is dump more fuel into an already rich cylinder.

Keep us posted.

[libbydiesel]

It sounds like the pump is 180° out.  Maybe it has the sprocket with two holes that fit the pump pin and they used the wrong one.

[air-cooled or diesel]

just because you jumped the glow plugs doesnt mean all are working, swap in a new set, bosch.
maybe air in system, bubbles if you still have clear line?

[vanbcguy]

Glow plug operating is simple to verify. Trigger the glow plugs, then touch the terminal end at the bus bar. If they are working they will be warm. If they aren't they will be cold.

[fatmobile]

I don't think bad glow plugs give you black smoke,...
 maybe white.

[ORCoaster]

Well if and when you get it started it belches black smoke the fuel is turned up to high on the adjustment screw on the backside of the right hand side of the fuel pump.  Not being able to keep an Idle makes me think that too is messed up so I am willing to bet that someone "messed around" with the throttle arm, the idle adjustment and the fuel screw.

But all of those affect the running of the engine and not so much the starting.  IF you are jumping to the glow plugs from the battery then you are getting around the circuit that normally makes that happen.  But is the final result, making the plugs actually glow, actually happening?  Pull each GP and jump it across the battery.  Do not hold in your hand or place on anything that will melt.  They glow red and will burn anything they are touching.  I lay them on the metal shelf in front of the Radiator and hook jumpers on them their.  If you have some that are damaged or broken apart, replace em, metal parts in the cylinder are not necessary to make the car run.  You can test them for resistance in the engine block but you have to isolate them by taking off that copper strip that joins them all together. 

Getting back to the hard start part.  If the GP's are all good or new and it still does that hard start then I would be looking at the fuel delivery first and the compression in the cylinders second.  If you are sure there is no air in the lines, verified with a clear hose at the inlet and outlets then the other possibility is that it just isn't developing the 480 PSI the engine needs to make the fuel go bang. 

If you get it running again do you have a lot of smoke coming out of the vent tube that comes off the top of the engine?  Or down low where the brake booster line goes in?  Or do Jetta's not have that?

Those are the places I would look for what you are describing as a two fold problem.  This is not a gasser so don't think the black smoke is too much choke on the engine when starting.  The diesel is different in that way.  There is no choke on the engine, just an advance timing control, Cold start it is called.