[Vwdiesel] 93 EV DSL fuel filter Q

[rOLf peCHUkas]

hey all
I have a '93 EuroVan Diesel running on vegetable oil
yesterday I did some fuel line re-routing that screwed things up when  
I'm running on diesel and I want to understand why
the fuel filter on the DSL (maybe the gas too) has regular in/out  
ports for lines from the tank and to the engine
but it also has a little plastic valve cap thing that the return line  
from the injection pump runs through on its way back to the tank
I re-routed to DSL return yesterday to backflush the veggie filter  
when I'm running on DSL
and capped the barbed fittings on the little plastic thing (temporary  
work to see if it would function - just capped the ends with  
electrical tape)
and temporarily left the return line to the tank un-terminated - just  
open to the air
now when running on DSL IP (injection pump) is fuel-starved
runs OK on DSL at idle but on the road it dies
runs fine on veggie
I'm guessing that under load IP is working harder/pulling more  
strongly and may be sucking air through the electrical tape on the  
filter return cap
DSL line is indeed filled with air
but my question is:
IF the plastic thing is capped tightly
SHOULD the IP be able to pull DSL from the tank (and push return  
backwards through the veggie filter)?
or is it important for return to be routed through the filter so that  
IP can pull from the return line in a loop (this would presumably  
make things a lot easier in the IP)?
does anyone know if that plastic return fitting is designed to remove  
air from the return line or allow loop flow or both (or something else)?
but the basic question is: can the VW IP function properly with the  
DSL return going someplace other than through the fuel filter
?
thanks for any insight
-- 
Rolf Pechukas
Cambridge, MA