2000 1.9 tdi Jetta runs fine and starts quick but somtimes it won't start for a long time. Changed the fuel filter,n still soes the same thing everything ok then it won't start. I took the hoses off the fuel filter and had it crnk over and I did not see any fuel, maybe a little. When I hook them back up I can see the fuel start up the hose but still bubbles. Any suggestions.

SOURCE: 2004 jetta tdi wont stay running acts like running

It's very possible the fuel pump is going out. Same thing happened on my 2001 New Beetle about 6 weeks ago, until it finally would not start at all. I have the software and dongle for reading the computer codes, and the failure modes described led me to the fuel pump.

Depending on how handy you are, you can remove the fuel pressure regulator on the fuel rail in the engine compartment. Cover the regulator base on the fuel rail with a rag, and have someone turn the key on for 1-5 seconds and note if fuel consistently pumps out of the base. BE CAREFUL AND DO NOT HAVE ANY OPEN FLAMES OR SPARK IN THE AREA. Fuel is flammable, and there may be significant amounts pumped from the fuel rail.

SOURCE: 2006 Jetta TDI Stalls in gear

These little engines(although very good little engines)have a problem with carbon build up in the intake manifold. It builds up so bad it begins to choke the engine off. The only solution is to remove the intake and soak with a good solvent over night and will generally take you a good couple of hours to clean out to get to "like new" again. Once this is accomplished, it's like driving your car new again!!

SOURCE: 1995 Jetta: vacumn hoses missing causing car to miss...

A missing vacuum line will not cause a car to misfire, it will run rough because of un-metered air entering the intake system. A misfire could be from bad spark plugs and wires. A malfunctioning ignition system, a bad fuel injector or fuel pressure charging component. An end result for not correcting a misfire problem is a damaged catalytic converter. From the factory it should come with a vacuum routing label usually on top of the radiator carrier or hood locking system. It will tell you specific location for the vacuum lines.

SOURCE: working on a no heat problem on a 2002 jetta tdi.

Check again the THERMOSTAT VALVE!
Either u have placed it upside down or the temperature setting of that thermostat is too HiGH!

SOURCE: my 2002 VW Jetta tdi , wont start.Fuel shut off

The first thing to check is the intake cutoff valve. It's similar to a throttle body, but is usually fully open until the engine is shut off, then it closes fully to minimize engine shudder.
Sometimes carbon will build up in the bore where it sits, and after it closes it will not reopen.
It's the first part of the intake after the plastic tube from the maf sensor/air filter housing.
You can pretty much just put your hand on it and push around a little bit, and the spring will return it to the open position. It has an arm sticking out that is actuated by a vacuum solenoid.
I thought of this because you said it would not accelerate, and carbon also builds up inside the intake manifold, reducing airflow so much that it can't get enough to accelerate.

This is assuming that you've got a situation where the engine is cranking, but not starting.

Let me know if this helps or if you have more questions. They often have problems with the glow plug circuit, but this should set a trouble code.