assumptions:
I've got two tanks. One for diesel, one for vegetable oil.
Both fuel lines follow parallel paths, Tank> filter> solenoid valve (selector, where they come together)> lift pump> I.P.

The veggie side has hose on hose heat, and two electric heat elements, not that it is relevant. The diesel side retains the clear pre-filter, again, not relevant.

My question is.... since the veggie is being pulled through a larger filter element with greater resistance than the stock MB filter (veg filter is a racor diesel filter 600 series 2 micron), can I add a small lift pump at my veggie tank to push fuel along the line and add some positive pressure to the veg system without causing any problems to the stock lift pump, which would be down-line of the new lift pump?
new veg-side would be: tank (heated)> new small lift pump (napa?)> heated hose on hose line> racor filter (heated twice)> pollack valve > stock MB lift pump > I.P.
Return is looped into the post pollack/pre lift pump line, when on veggie- return to tank on petrodiesel.

Thanks for the help! I usually ask on the veggie oil forums for stuff like this, but this is more a conceptual question for MB diesels- OH, this is on my 603 in the 87 300SDL.

Thanks!!
Kevin

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Cannondale ST600 XL
Redline Monocog 29er
2011 Mini Cooper Clubman
2005 Honda Element EX

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Here is a link to a recent related discussion.
http://www.peachparts.com/shopforum/showthread.php?t=99077

If your engine were an OM617, I would say a definite YES, providing that the new pump provides up to around 0.8 Bar fuel pressure.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.