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Rob, I guess I'm a moron - you have an IDI, the whole 2 fuel pump thing DNA...

Soooo, my suggestion is get (3) 3-way solenoid valves - Frybrid sells hydraforce valves for about $75. These are very reliable electromagnet-operated valves that are easily dissassembled (in place!) and cleaned/repaired if necessary.

The 1rst valve will be before fuel pump/lift pump and will select what fuel tank ya pull from. Use an aluminum VO tank and a Hot Fox heated fuel pick-up. (search Artic Fox...) These pick-ups heat the fuel as it exits tank, you really don't want to heat the whole tank (causes condensation and polymerization/fuel degradation issues in the long run)

The 2nd valve will be after IP/injectors and will select which tank the fuel returns to. Don't use the typical 6-way Pollak switching valves - they don't hold up well in hot VO service and cause cross-contamination of fuels in the tanks (VO in diesel tank is not good!) This is why we use (2) 3-way valves, so we can delay the return valve switching back to diesel tank until after purge.

The 3rd valve will be on the VO return line and will select either return to tank or 'looped return'. The 'looped return' will send fuel back to the supply valve before IP. You need a return to VO tank for purging. When you purge, you'll pull from the diesel tank and return to the VO tank - eliminating VO from the IP and injectors. Also allows removing air from system after filter changes etc. (air is trapped in a 'permanent' loop)

I use a 10mic spin-on fuel filter and base by WIX - about $35 base and $7 filters and heat it using a 3/8" copper 'coolant wrap'. I had a modified soft-sided 6-pack cooler over this to help keep the cold air out/heat in.


I also use Mercedes aux. coolant pump (by Bosch = under $100) to insure good flow thru VO coolant loop. These engines (especially my PSD) are very cold natured and at low RPM's/low load (ie, traffic jam) I would see coolant temps fall dramatically - especially in cooooold weather.

You 100% do not want to share filters with both fuels - have a separate filter for each fuel. #1 - WHEN your VO filter plugs up, you really, really want to switch back to diesel and get off the RR tracks, mmmmkay? #2 - you can't ever get a really good purge when sharing filters, there is an awful lot of mixing goin' on in there. Take a full coke bottle and begin adding water until its clear and see how many gallons it takes!

So heat - heated fuel pick-up, TIH from there to (heated) VO filter, and if its under truck or otherwise not close to the supply valve, run TIH from there to FPHE. Yes, you'll still need a final HE unless you could run your 'looped return' thru TIH all the back to tank. Actually, if ya put VO filter under cab (about 1/2 way to engine), then you should have warm enough VO to be able to filter it and you could tee in the looped return directly after the VO filter. (ya really don't want to loop thru the filter if you can help it - filters will last ALOT longer) What you NEED is 160* PLUS VO before the IP, any less and you're not getting good atomization/combustion. Please don't use vegtherm or other electric heaters - they tend to overheat VO causing more problems than they solve.

I'm sure a picture/diagram of all this would have saved 1000 words, but I don't have the technology...

I used DiPricol Optix gauges, but no longer recommend them - the ISSPRO EV Series gauges are prolly the best, but Autometer makes much more economical gauges. I strongly recommend a fuel pressure gauge just before IP - it may save your IP one day!!!! Any one-wire temp gauge can be wired to several senders using a switch. Extra senders are like $10ea. There are 'controlling' temp gauges (Summit Racing) that have adjustable settings that usually turn fans on/off, but they're around $100. What you want is a normally-open 180* switch. This will close/complete the circuit at 180*. I'd put this in the coolant supply to VO loop (near engine) as long as ya have adequate heat in VO system - either FPHE or looooong looped TIH set-up. Monitor VO temp just before IP.

Here's the Excursion's gauges and VO system switches:


OK, a few words about cross-contamination and blending. Bottom line is the thicker-than-diesel VO will not properly atomize and therefore will not attain complete combustion. This leads to carbon build-up/coking, often at ringland (coolest place in combstion chamber), which ultimately scores cylinder walls and damages valve seals, etc - but often coats the injector tips first furthering poor atomization... Keep in mind, the engine 'runs fine' while all of this is quietly going down! If thats not bad enough, there is the blow-by standard in ALL high compression engines like diesels. Before the engine reaches operating temp, some combustion gasses slip past the rings and enter the crankcase. When this is diesel, it very slightly dilutes the oil, and the soot present turns it BLACK. (now ya know why yer oil turns black so fast!) When this is VO, very bad things happen. The VO will rapidly polymerize in the crankcase environment and as it does, it looses its ability to lubricate stuff like its supposed to.

One more thing before I crawl back under my rock, if you drive much (and you totally WILL when your cheap-fuel vehicle is reliable!!!!! ) you will totally get your money back - I promise. I have met so many people who tried to 'save money' and 1/2 baked a 'conversion' and either damaged IP's/injectors or worse! or ended up spending more in the long run than if they'd just done it right the first time. No exaggeration - I drove 70k miles on my original conversion and never so much as tightened a hose clamp, much less changed/modified anything. Hell, I've saved almost enough now between the 2 trucks to pay for the Excursion AND its VO system!!

feel free to PM me if ya have questions.