Hey, I have never posted here before so I hope this is the right forum group to be posting a troubleshooting question in...please forgive me if it is not.
Anyhow, I have a 98 TDI with a Greasecar conversion system, including the veggie computer.
My car has sat for the last 6 months as the timing belt blew destroying engine etc and just now getting it running again, in case that is informative in some way. (lots of random things stopped working in the hiatus).
Ran veggie fine for 50 miles or so, then when switched it off the return valve stayed stuck on and dumped all diesel from tank into veggie tank, coming terribly close to spilling into the trunk.
At any rate, could only troubleshoot on side of road (with no multimeter) and ended up switching back to veggie and getting to gas station to add 1 gallon fuel to diesel, letting some burn off before purging and switching it off for the night.
I have a steel veggie tank in the tire well in trunk.
Okay--so here is my question and possible diagnosis, please let me know if it's a possibility so that I don't need to order new valves:
Is it possible that a vacuum is being formed in the steel tank that is overpowering the ability of the return valve to switch itself back to diesel?
I wonder this because if I even drive a few miles on veggie and I attempt to open the tank filler hole it's like I have to fight against enormous pressure and then it makes a popping/splash sound.
(I gather the air vent hole might be clogged?)
Also, historically, it's like the car struggles for fuel sometimes if I've driven a number of miles on veggie, and if I pop open the tank to let the air go in it seems to run much better--at least for the next dozen or so miles.
Anyhow, the car is perilously low on diesel and perilously full on veggie, so really don't want to end up running out of diesel cause of a stuck valve or flooding trunk (which I've done in the past and really really do not want to do again).
Does this sound plausible, or is it more likely to be an electrical/grounding/some other issue?
