Air bubble in fuel line

[wild3bill]

I was driving my 2003 Golf today when the engine died suddenly. It felt like a no fuel problem. I had about 125 miles on a full tank. After I stopped I looked under the hood, I noticed an air bubble an inch or so long in the clear fuel line at the high point where the pair of fuel lines between the fuel filter and the injection pump go over the hump of the timing belt cover.My older pre TDi VWs some times had problems and got bubbles in the clear fuel line, but they were able to limp home, and I could restart those older engines. The 2003 needed a tow home! Any suggestions on what happened and how to fix it?

[Fatmobile]

Probably a fuel line restriction,..
probably a clogged filter,...
maybe the pickup screen in the tank is clogged.
What's the fuel filter look like?
Does the line running next to it; heading back toward the tank go back to the filter.
Some VWs have the return line go back to the filter and circulate warm diesel,.. there is an o-ring that can sometimes leak on these setups.

[wild3bill]

Black return line next to clear line passes through a T fitting in the top of the filter(held in place by a wire Mickey Mouse clip) I drained VW filter into a glass jar, the drained diesel looked pretty good compared to stuff I haverained from older filters in older VWs. Next I would suspect fuel lift pump.

[wild3bill]

Old Diesel filter looks clean enough to put back and use another 3000 miles.
I can draw fuel through line with a small external pump. And pump it through the new filter. The injector pump does not accept the fuel. Engine cranks fine but does not start. If injector pump was injeting fuel Engime would run or at least emit a little smoke.

[Fatmobile]

I don't know much about TDIs.
If the injection pump wouldn't accept fuel (on an IDI) I would suspect a clogged "OUT" bolt screen.
That's the only thing I can think of that would keep fuel from pushing through the pump.

That wouldn't cause air in the fuel so,...
Was the fuel line hooked up to the injection pump when you tried to push fuel through the filter? Basically wondering if you checked the flowablity of the filter seperately from the injection pump,.. if you pumped fuel through the filer without the pump hooked up.
I'm still suspecting the filter, even though the diesel looked good.
Curious what you mean by it looks good. Our Rabbit fuel filters don't open so you can see the element, does the TDI?

[wild3bill]

The exterior of the old filter looked kind of new, it was the fuel I drained out of it into a clean glass jar that looked clean/good. You can look into a TDi filter through the hole where the Tee fitting in the return line hooks to the top of the filter.
Now I suspect Shut off valve/solenoid failure!

[wild3bill]

The airbubble does not seem important.The immobilizer or the Fuel shut off (valve/solenoid) May be culprits in my non running TDi's
There is no lift pump out back no water separator other than the filter either:
No blockage or clog or air in leak in theline from my tank to the injector pump where the fuel may be shut off by the shut off valve or it may be immobilized!