I have a 2000 VW Jetta with a home built two tank SVO conversion. I have been driving it with no trouble since I converted it in 2007. This week I have had several strange things happen. I was driving with the SVO tanks somewhat low, and going down a fairly long hill. Part of the way down the engine died, I had had this happen before and I simply switched back to diesel fuel and let the engine restart by compression. I pulled over when I got to the bottom of the hill, to check my tank, as I didn't think that I should be out of SVO. When I stopped I turned of the engine because I waited to check that the solenoid valve was switching properly and it can't really be heard over the engine. When I tried to restart the car, it cranked but acted as though it was out of fuel, which I knew it wasn't, as I had switched back to diesel. I had to loosen the fuel injector lines and crank the engine in order to restore fuel flow to the engine. I didn't have any other problems that day.
This morning I was driving into town, and part of the way there, after I have been switched onto SVO for a while, the engine started hesitating, and acting like it might stall, I switched back to diesel and the problem went away. A bit later I was able to go back to SVO and didn't have a problem.
Tonight on my way home I had to make a brief stop, as I knew I would only be parked for a minute, I didn't change back to diesel fuel, I have always done this, and never had a problem before. Tonight when I went to restart the car it did the same cranking-but-not-turning-over thing that it did the other day. This time I was able to gt it running by compression starting it, but all of this has left me with the idea that something is very wrong.
Any ideas of what might be wrong/how to correct it would be welcome. I'm fairly good at working on cars, but I don't have that much experience at troubleshooting them.
The only change I have made at all recently is to swap the DPDT switch that originally came with my fuel selector valve for one that had a center off position. This was to address that fact that the way the valve and switch were wired the solenoid was constantly drawing down the charge in my battery when the car was parked.

Thanks,
-Joe

Sounds like air in your veggie lines to me.

I have some more information. After making my previous post, I was looking around under the hood of my car, and found that the spin on filter for the SVO was leaking a bit because it was not tight on its base. It is inside of a heater hose wrap and I haven’t done anything to it since I converted the car, so I guess it must have vibrated loose over time. I guess that would mean that you were quite right Graplr, thanks very much. Incidentally, about how often should the spin on filter be replaced?

Hi Joe
I have an 03 TDI and I replace my filter 2 times a year just because. They are cheap and preventative maintenance is better that troubleshooting on the side of the road. My friend had the same situation where the filter company made a slight change in the filter design and he sucked a little air at the filter head.

quote:

about how often should the spin on filter be replaced?

You should consider adding a vacuum gauge to your system to help trouble shoot issues like this. It will tell you when your filters are starting to clog, if your switching valve is working, i fyou have air in your fuel lines, and provide other useful info.