Parallel Fuel System

[Begle1]

I have an auxiliary fuel tank for veggie oil, and an auxiliary set of filters for veggie oil, ready to be installed.

Since I'm using veggie-dedicated filters, I have two options:

Number one is to use the stock lift pump for both fuels. This way I'd need three switches; one before the lift pump to select what tank I want it from, one after the lift pump to select what filters I want to use, and one after the injection pump to determine what tank I want it to return to.

Number two is to get an auxiliary electric pump and keep the two fuel systems separate all the way from the tank to the injection pump; the veggie goes from the tank, through an electric pump, into filters, into the injection pump. If I did it this way, I'd only need one switch (to select the return path).

But If I go the second route, and spend most of my time running with an electric lift pump, what do I do with the stock lift pump? Can the stock lift pump be ran for tens of thousands of miles without actually flowing any fuel?

Is it designed to do that, or would it overheat and over-pressurize and blow itself up in a hurry?

[PToombs]

Can you put a bypass valve on after the LP? So when you flip your switch, it passes fuel direct back to tank?
I thought you had to go back to diesel before you shut down, and start on diesel when running straight veggie?

[Begle1]

If I can't run the stock lift pump without it flowing any fuel, I think that some sort of bypass would be the only way to get away with it an electric auxillary. But if I have to add some sort of bypass then that'd make things as complex as using three valves...

I'm going to have heated veggie line and filters all the way to the injection pump inlet port; I'll start on the stock system (altough in Phoenix I probably wouldn't have to) to warm up the auxillary fuel system. Then you're supposed to swap over to the stock system again before you shut down in order to purge the veggie; since I'm not going to be purging filters or lines, only the injection pump, I should only have to do it for a couple of seconds.


Oh yeah, and whatever I wamperjaw together is going to have to be hot-swappable too...

A benefit of the full auxillary option is that I could run #2 and veggie at the same time... Which might be worth it just for novelty's sake.

[wannadiesel]

Uh, if you ran 'em at the same time you'd be dumping veggie oil into the diesel tank via the return.

I like the idea of having the veggie system completely isolated from the stock system. That way if you get a plugged filter at 3 am in the rain you can flip a switch, drive home, and deal with it later. Dead ending the lift pump isn't a good idea, though. I suggest teeing into the supply line to the IP and running a hose from there to the return line, with a solenoid valve inline on the hose between the supply and return. When the system is in veggie mode, the stock lift pump would just sit there and recirculate the fuel in the tank.

[Begle1]

How do you have your Walbro plumbed in?


I'll have to draw a picture in MS-PaintCAD to see what I got to do...

[PToombs]

I suggest teeing into the supply line to the IP and running a hose from there to the return line, with a solenoid valve inline on the hose between the supply and return. When the system is in veggie mode, the stock lift pump would just sit there and recirculate the fuel in the tank.

That's what I said!

[wannadiesel]

How do you have your Walbro plumbed in?


I'll have to draw a picture in MS-PaintCAD to see what I got to do...

Mine feeds straight into the dirty side banjo bolt on the filter head.

[Begle1]

Alright, so here's what I've got...



If anybody could think of a way to simplify that any I'd be appreciative.

Anybody have any experience in two-way, electronic valves like I'm going to need?

[fergavs]

I have used them a fair amount in air bag set-ups. Are you just using 1/2" 12v hydraulic/pneumatic Valves? They are pretty basic , ground one side and 12v to the other. They are labeled for direction of flow.

[Begle1]

I guess that's all I'm using. Whatever it is has to be good for, oh, 20 PSI of fuel at 220 degrees to be on the safe side.

Who's somebody that makes them?

[wannadiesel]

Looks pretty darn simple. You are going to set it up so that the return goes to the veg tank for a minute or so after the switch back to #2, right? It's much better to have some diesel in your veg than some veg in your diesel.

[Begle1]

I don't know what happens if they mix in small amounts... I think they'd diffuse and it wouldn't be a problem. I don't think it'd coagulate, would it? I got an "F" in chemistry...

[PToombs]

That setup looks pretty straight foward to me. You can check Graingers, http://www.grainger.com/Grainger/wwg/start.shtml for valves.

[wannadiesel]

I don't know what happens if they mix in small amounts... I think they'd diffuse and it wouldn't be a problem. I don't think it'd coagulate, would it? I got an "F" in chemistry...

Pumping veggie into your diesel contaminates the diesel you are using to flush the system to prevent gelling and deposits. You want to keep the diesel clean, if you have a good supply of WVO you might run around for 6-8 months on the same tank of diesel.

[CAJUN 93]

what your building is a frybrid kit. veggiesel has one installed on his truck. those of you who were at the kentucky meet saw it. i'll tell him this post is here and see if he'll get involved. he's done a lot of research on alternative fuels.

daryl