My first step was to install clear fuel line on the intake side of the injector pump. Started it up on diesel, no air bubbles. Drove it until warm then switched to looped veg; still no air. Drove for another 10 minutes or so, to the point where the engine was starting to clack and misfire slightly, like it had been doing before (see this thread for more on that: viewtopic.php?t=5573&sid=07c25121d75894 ... 1d7eea0307). I went and looked under the hood thinking the looped system would be full of air--but no, it was pure clear fuel, no air at all. I guess that means that the seals are tight in both the fuel line connections, and in the injection pump, because obviously there was no air in the return either if there was no air in the intake line during looped fuel flow. I did notice that if I pulled the cold start advance knob out part way, it got rid of the clacking.
My biggest surprise was that the clear vinyl fuel line did not feel nearly hot enough when running on veg. It was warm enough to make the vinyl line softer and mushier, but definitely not hot to the touch, as it should be if the oil is really at 120-150 degrees, right? The metal fuel injector pipes didn't feel real hot either. Maybe my problem is just that my veg oil is too cold--the Greasecar system only really heats the fuel by running it through a heated filter when in looped mode, since it pulls so slowly from the HIH tank line (which is very hot) and gets most of its fuel out of the pump return line. Just heating the filter seems pretty inadequate to me, and there's also a long distance that's not heated between the filter and the injection pump. How hot does the inlet line feel on your guys' SVO systems when running in looped veg mode? What kind of symptoms do you see when the oil is too cold? I figure that if the oil was too cold, it would not atomize properly and would then combust more violently, like what happens with diesel when the engine is cold, and that's why a little timing advance would seem to clear it up. Sound correct?
This is on an engine that was rebuilt only 9000 miles ago, and is known to have perfect compression, no overheating, good power, no oil or coolant use, etc. The injector pump is original with 234,000 miles, but it does not leak and the car runs great so I don't have much reason to suspect it. Injectors were rebuilt and calibrated when engine was done. The WVO system is a stock Greasecar kit with 15gal rectangular aluminum tank, hose-in-hose fuel line with hoses run through the interior, looped return with purge, and heated fuel filter. See pictures of the whole setup below.
My inclination is that the oil might just need some kind of final heat device. I guess the options are a flat-plate coolant heat exhanger or a vegtherm before the IP, or some of those individual electric fuel line heaters for the injector pipes--any suggestions there? I'm still stumped as to why it takes several minutes of running on veggie for it to start to have problems, but maybe that's just how long it takes for varnish to start to build up or something.
Thoughts? Suggestions? Anything helps. Thanks in advance.
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