i'm getting a high reading on my vacuum gauge when i run diesel...but not when i run veggie. i temporarily bypassed the fuel/water seperator (only diesel runs through it) and undid my gas cap (in case it was a clogged tank vent) but the gauge is still showing that i have resistance when i'm on diesel. here are my two questions

1) i haven't changed the stock filter yet (both veg and diesel run through it). i did change it about 1000 miles ago, but assume that its fine since i don't get resistance when the wvo flows through it....unless wvo is more viscous than diesel when hot??

2) is it possible that wvo thats gotten into my diesel tank via the return lines when i switch back has finally accumulated to the point where its clogging an unheated diesel line like a clogged artery or something?

any other ideas on what i should check??

 

for clarity, i might suggest you mention that the vacuum gage is on the fuel line to show restriction, as was talked about in the other thread.

that said, your point #2 is a very likely cause of your issue, but i've also heard of guys having issues with the pickup foot in the tank decomposing and becoming debris that clogs the fuel line. it might be wise to disconnect the line from diesel tank to selector valve and blow it out with compressed air to eliminate any chance of problems there.

many guys who run WVO run two seperate tank selector valves, one for supply and the other for return. when the flip from diesel to WVO, they flip both valves, but when they return to diesel, they run for 5 minutes or whatever pulling straight diesel but leaving the return lines to the WVO tank. this obviously prevents the contamination you might be suffering from

 

well my diesel tank is usually only ever a quarter full. topped it off today and the problem went away (or at least is out of sight out of mind). maybe i have some oil floating on top and when my tank gets low i start sucking unheated oil out.

 

I'd say that unless you have a clog, the only thing that would account for a vacuum difference between diesel fuel and veggie oil is the viscosity. As long as the viscosity of the two fuels is equal, your vacuum should read the same. Are you not heating your oil to the recommended temperature (I seem to remember ... 175 degrees F or so?)

 

i heat my veggie tank/lines but i don't heat my diesel tank. right now, every time i switch back to diesel the veggie in the return line ends up in my diesel tank...where it is unheated. i think enough of it accumulated to cause a little sluggishness. i'm assuming that oil floats on diesel and that by filling my tank i pushed the oil up out of reach of the fuel intake line in the diesel tank...therefore delaying my having to deal with the problem.

after my valve, the supply lines are all heated, so there really is only five feet or so of diesel line thats unheated. maybe if i wait till summer i can run the diesel tank out with minimal harm. otherwise i guess i'll drain the diesel tank...

 

Ruh-roh. Yeah, I think that's why everybody recommends a 3-valve setup, so you purge your lines back into your veggie tank. It'll contaminate the veggie tank with a bit of diesel fuel, but not the other way around.

Maybe just add some in-line heaters before your IP, so regardless of which tank the fuel is coming from, the fuel gets heated? Or hose-on-hose from the selector valve up to the IP.

 

yeah. i'm hose on hose from the valve to the IP (for the most part). the stock filter is shared (diesel/wvo) and has a heat wrap that is only on when i'm on veggie though...so thats a weak link.

now i know why everyone pushes for the three valve set up.....

 

Classic symptom of the foot in the bottom of the tank being bad, either the flapper valve on the foot or the foot itself being bad. This issue causes air in the fuel system from diesel.

 

This is a typical problem for half-assed conversions. The WVO contaminating the diesel tank has likely plugged up the in-tank filter/screen. Unfortunately, this is (was?) just the beginning of the problems with the 'cheap conversion' concept.

That same oil that is creating a high vacuum is also being left in the IP and injectors every time ya shut the truck down - slowly polymerizing its way to carnage. If the IP survives this torture long enough, the coking/carbon build-up in the combustion chamber from starting the engine on this cold VO (off the bottom of the D2 tank as well as what is left in the D2 filter) will ultimately create doom and gloom. Of course, if you are putting WVO in one of the stock tanks - that'll likely be a problem first...

Its not that hard to burn WVO 'the right way'. Use (2) 3-port switching valves instead of the OE 6-port valve, so you can stagger the return fuel and put the VO/D2 mix into the veggie tank instead of the D2 tank. This along with separate filters for VO and adequate heat (heated fuel lines & FPHE) only costs about as much as a few tanks of D2.

Good luck and keep us posted!

 

its magic , idi's will run on sun tan lotion. or any oil like substance, with a cetane between 42 and 70,