Alright, i've figured out why the link wasn't working now on to try and resolve the issue: Fuel contamination?
Ive attached the fuel line schematic so we can all be on the same page. And please correct me if at any point im wrong. My understanding is that in the stock configuration:
fuel comes from the tank to the thermostat/heater 155
032 is the line from the thermostat to prefilter screen
next 056 is from prefilter to shut-off valve
then 074 is from shut-off valve to lift pump
then 083 goes from lift pump to fuel filter
from the fuel filter 095 goes to shut-off valve
the shut-off valve has an open port on rear that fuel heads into the IP from
Excess fuel from IP travels along return line 119 which meets up with the excess fuel from the injectors and the filter this is a 4 way open fitting.
OK, so this outlines the stock configuration.
I feel that there must be some significance in designing the shut-off valve to have fuel pass thru it from the prefilter to the lift pump.If there was not they could have just designed a shutoff between the filter and ip which is also where temp is measured?
So assuming that the shut-off valve allows for two seperate fuel paths 1)from the prefilter thru the shut-off to the lift pump and 2)from the diesel filter thru the shutoff to the IP... for any fuel to cross contaminate it would mean that fuel that hasnt been filtered by the diesel fuel filter would be entering the IP which MB would not allow...

Im replumbing for a VO system I have isolated the return so that it does not reenter the diesel fuel filter. Excess fuel from the injectors and IP meet and are directed to a valve selecting diesel or VO tank return.
Next to isolate the supply systems i have replumbed a few of the supply lines. My current schematic is Diesel fuel from tank to thermostat to prefilter screen thru the shut-off valve to diesel filter out to a selector valve which then goes to the lift pump back thru the shut-off valve and into the IP... The vegetable oil side then comes from vegetable oil fuel tank to vegetable oil filter to the selector valve then follows the same path to the lift pump, thru the shut-off valve and into the IP.

Because i have isolated both the return and supply systems i should have minimal cross contamination. My quest in discovering the inner workings of the shut-off is to make sure that is indeed the best possible fuel plumbing for this vehicle. Also to find out if there will be any negative side effects to only passing the vo thru the shut-off valve once as MB felt the need to plumb diesel thru it 2x.

Sorry if thats alot of info at once. All your help is much appreciated.
Thanks

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