AltFuel Hmmm, 3B WVO purge time thoughts.... (1 Viewer)


That's not rust, it's Canadian patina...
Nov 11, 2005
~Kingston, ON, pero soñando de Panamá
So the other day I'm thinking about where I will be connecting the WVO system to the Diesel system.

The current plan was to remove the existing diesel line from the input to the fuel feed pump (mounted on the side of the injection pump).

A friend mentioned it would be better to splice into the hose going FROM the factory fuel filter, as it would greatly reduce my purge time. (he is not a toyota diesel guy). As true as it is, AFAIK without running through the feed pump, I would not draw any WVO from the tank - so I think that's out of the question (unless I installed a seperate pump)

So... that got me to wondering what my purge time would be...

Lets just say the stock filter is 0.5L volume, and the FP, IP & lines are ?0.5?L. This would mean I need to flow 1L of fuel to purge the injector lines of VO. Then I got to wondering how long this would take.

Very roughly, I seem to get about 14L/100km (70L gets me about 500Km). So, My figuring... if driving at 100km/hr I go through 0.23L per minute (14/60). If I need to purge 1L, it will take me approximately 4-1/2 minutes to purge the system (1/0.23 = 4:35)

That also means that when switching from diesel to VO, it will be 4:35 before I am actually RUNNING on VO!

35 minute drive, 5 minutes to heat up, 5 minutes to start flowing, 5 minutes to purge at the end, gets me 20 minutes of actuall VO running time... (until I really NAIL the time it takes to get the engine up to temp, and I can actually switch over before I'm up to temp because I know I'll still be running on diesel)

So that is about 57% of my commutes running on VO - not great, but still less than 1/2 the price it costs me now!

So... how is my math? does anyone know what the actual volume of the engine components are? (filter should be easy to figure out, but how about the rest?)

The only simple way I can see of getting around this, would be to use a pair of 3 port valves, one before the feed pump, and one after it. If the valve before the feed pump is on diesel, the valve after the feed pump goes to the filter. If the valve before the feed pump is on VO, the valve after goes into the IP.

Am I making less sense as I go along? Should I just live with long purge times?
Apr 12, 2008
My friend and I are currently converting a 3B to veggie and I've been thinking alot about the valve configuration.

First, the pump will push much more fuel then the engine needs even under wide open throttle, in fact, via the engine manual the feed pump should be providing .9 L/min. This is compensated for via the return/leakage pipe on the injectors which goes back to the pump. The key for fast purge times is to eliminate this return flow via a 3-port valve at the rubber portion of the return pipe, off the no. 4 injector. Also, having two 3-ports allows back-flushing of the veggie line with diesel so that when you shut down no portion of the line not exposed to coolant heat is filled with SVO.

I think that we are going to splice in the supply 3-port just before the feed pump and allow the stock filter to be exposed to both diesel and veg but have second dedicated, heated filter on the veg supply side as well (this filter is pre-valve). I would NOT bypass the stock filter after the feed pump even with a second filter pre-pump, Toyota put it there for a reason which is most likely that the feed pump itself will create metal shavings and junk that isn't friendly to IP (even inline ones). The rule of thumb is nothing but fuel line should be between the filter and the IP.

With the config. I've outlined I think that you'll find your purge times to be much faster. I have about a 40 second time on my 2LT-II with pretty much the same setup. On shut down just hit supply to diesel and leave return on veg to back flush to the filter and eliminate any oil in the lines. I've think that with 2 3-port switching over is nicer as well as the fuel is slowly mixed when you first hit the switch as returned diesel mixes with SVO. Given that it sounds like you'll be doing the same drive repeatedly, you should be able to get a feel for when you are up to temp and may be able to "cheat" by anticipating when you'll be on pure SVO making your switchover times that much shorter.

Hope this helps,

Dec 10, 2003
awesome timing

I'm at exactly the same stage with my 3B WVO build up so your comments could not come at a better time as I unlike yourself do not have a 3B shop manual.
I was actually thinking of 'T'ing in b/t the IP and the filter. I'll definitely consider your comments.

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