i am in the process of modifying my fuel lines in order to run one tank off of veggie oil. i'm curious why the fuel return from the injectors is returned to the tank instead of looped back to just before the injector pump and teed into the supply line. is there a reason the excess fuel needs to flow back to the tank? can i modify the fuel system descibed above without problem?

 

Air bubbles will inevitably get ito the fuel system. The return line is there to get those out of the injectors before they make the engine die. Also, hot diesel is a poor lubricant, so returning most of what is pulled into the IP helps keep it cool, while making sure that the fuel in the tank is not gelled.

You 'can' loop the return line, but you will want to have some easy way of removing air that gets in the system. I'm toying with putting in a solenoid to either return the fuel to the tank or loop it. That way I can keep regular diesel cold, and also keep vegetable oil hot, and I can jst open the return line every so often to purge air.

 

thanks for the insight, teedo. i was reading "from the fryer to the fuel tank" and the return line routing is what he suggests. i knew there was a reason for the returns to the tank.
i haven't yet started to run veggie oil; i've begun to collect from restaurants and everything is in place with the electrical & coolant , however i am waiting for the kit i ordered to repair my return lines at the injectors so i can do everything at once and not have to bleed the fuel system twice.
how is your conversion running?
how do you collect/filter the oil you get? i got a gear oil pump and filtering "wand" from neoteric for collecting & transfering that works *great*. if you were interested in part #s etc. let me know and i could tell you where they got everything from.
it was interesting for me to see in the book a graph that compares the viscosity of veggie oil with the viscosity of diesel fuel, and that veggie oil matches the viscosity of diesel at 160 degrees.
hey you know another question i had that you might be able to answer: how long do you run your engine after switching over before shutdown? a couple of weeks ago i switched tanks (both holding diesel even) a couple of minutes before shutting down and when i went to start it back up again it wasn't turning over. i had to manually bleed the lines. do you know of a pump that attaches to the schrader valve on the fuel filter for bleeding the air out?

 

If it didn't start up right away is sounds like you might have a air leak in your solenoid. Last time I drained my stock water separator, I got air in the system, which I've heard is a common problem, but I haven't heard of people having air leaks from the solenoid. I suppose it's possible that there's a bad seal. Also, if your fuel filter is't screwed on tight, it can leak air in. My Haynes maual says to only hand tighten, but that's nonsense. Just don't overtighten.

Yeah, I bought "from the fryer to the fuel tank", too, but I think it's outdated. Hose-in-hose isn't necessary, and is much more prone to leaks than hose-on-hose. As far as looping the return, I think some vehicles are better with it than others. mercs probably have no problem passing an air bubble or two, but I think our fords are prone to just dying if they get air.