I was trying out some blending in my Jetta GL, after about 2 months I wasn't happy with the way it was running so I pumped out all the veg and filled up with my B100 which I ran previously without issue. The car had sat for a couple of months and now won't start.

I think the first thing to do is replace both filters and try again, I have pushed 10 psi compressed air through my fuel supply line to free any obstructions. Anything else I might have overlooked? Obviously pumping out the fuel tank left a liter or 2 of veg. When I filled with B100 I ran the motor for a few minutes hoping to leave her with B100 in the lines.

I would check you don't still have an airlock-crack the nut on the injectors slightly to see if fuel is getting that far-might have a vo block somewhere-otherwise check you have glowplugs-my guess would be air somewhere
good luck

Any Luck?

I'd second the idea to make sure you are getting fuel flow.

Do you have a transparent hose from the fuel filter to the Injection Pump? Any air in the line?

One of my Caddys has an auxiliary fuel pump hooked in back near the tank. The nice thing about that is that it circulates the fuel quite well and will purge the line of any air quite quickly.

Obviously, bad glow plugs will make the engine very hard to start. They are a major hassle to get to on the Caddy, and the bus-bar makes it hard to isolate individual glow plugs. I'm still learning, but the "poor-man's tester" is that if they pull amps, they should be good. I.E. If you touch 12V+ to the end of each one and get a good spark, you are probably ok (or if you pull them, test them with 12V to see if they pull power and heat up almost instantly).

Starting Fluid seems to cause the VW cars to kick a lot... I guess you have to be careful with that one.

My Tractor seemed to like a heat-gun blowing into the intake (until I got the IP fixed and glow plugs replaced). Be careful around plastic though.

I'm working on trying to get an old Ford Pickup started. I believe that it sat for a couple of years with either leaky injector return lines, but more likely a dry fuel pump and dry injectors. And, I've come to the conclusion that is very very bad for the vehicle.

When was the cutoff for Natural Rubber vs synthetics in the IP seals? '95 sounds like it could be on the boarder.

Finally, make sure the engine is cranking over at a good clip, or give the car a good push (assuming you have a manual transmission).

Good Luck,
Cliff

I pumped the tank again and put in some diesel and replaced a fuel filter and she fired up.
Smoked and coughed at first but now sounds like she always did. Yippee.