1993 GMC Sierra K2500

A description and pics of your SVO WVO Vegetable Oil conversion, help the next person who gets that model.

Moderators: SunWizard, coachgeo

1993 GMC Sierra K2500

Postby VegMeister » Tue Mar 25, 2008 12:53 am

... with long box, ext. cab, 6.5L engine, manual transmission.

I plan to post up some pictures when it stops snowing.

For a schematic of the basic idea I used, see this thread.

Tank: 74gallon aluminum transfer tank/toolbox combo, Delta brand, on sale at Fleet Farm

Electric pumps: kept the stock diesel pump, used an OEM AC Delco replacement model for the veg pump. Both pumps have check valves, which is REALLY handy and I'm pretty sure I need it for my system.

FPHE: 12 plate, good quality

Veg filter: spin-on goldenrod, Dana Linscott modifications.

Lots of fittings, valves from home depot, I always tried to fit things directly together using close nipples to save space.

3-way valve: got it from an older guy. 20$, he had had it in his garage for years and years.

Fuel lines: 3/8 I.D. fuel lines.

Coolant lines: 3/8 I.D. fuel lines, except the part from the engine to the FPHE, which was 3/4.

Coolant plumbing: I unscrewed the fitting for the heater core. It's right on the top of the front of the engine. I then cut off the first 10 inches of hard aluminum heater line and replaced it with: 1/2" close nipple, brass T and 1/2" ball valve (for controlling the flow of coolant to the cabin). On the other side of the T I put another ball valve and then a 3/4" barb. 3/4" hose goes to FPHE (on the airbox), I have a 3/8" line going from that, wrapped all around my veg filter, and then through the firewall, under the driver's seat, and out the back of the cab to my heated pickup. It then returns the same way and goes between the airbox and A/C and into a ball valve, which has a T into the 5/8" return coolant line (the one that goes from the heater core and returns to the radiator).

Diesel fuel plumbing: lift pump is stock, on the frame rail under the driver. Filter is stock. The only modification is that I cut the fuel line going from the filter to the IP (to splice in a T). *note* that is a PITA to get on there, after fighting for 2 hours I realized it would be easier to use a little tiny wrench to loosen the clam on the IP, pull the hose right out of there, stick everything on the T, and then reach all the way in there, put the hose back on and very "trickily" tighten the clam again.

Diesel fuel return: I just cut the return and spliced in a 3way manual valve. The return runs RIGHT next to the firewall, I was able to drill a hole for the handle ... I removed the knob and put it inside the cab and re-attached it to the valve.

Veg fuel plumbing: from the heated pickup, into the cab, under the driver, through the firewall, into a T (which is of course connected on the other end to the 3-way valve, remember my system is a looped return some of the time), into a ball valve, and then fuel line takes it to the FPHE (mounted on the airbox), fuel line takes it to the veg filter (mounted on the top of the firewall, to the right of the lift pump relay), and then through a temporary filter and then into the T between the diesel filter and the IP.

Veg fuel return: if the 3 way valve is in the right position, return goes into the T that is between the ball valve and the line that runs back to the veg fuel tank. This makes it a looped return. IF you have the diesel pump running, you can close the ball valve to PURGE the system to the veg tank. Keep in mind that you should try not to run in purge mode without switching to the diesel lift pump, because then you IP will not be being supplied with fuel and will be forced to pump diesel all the way up from the diesel tank.

Wiring: there is currently only one switch on my truck. It's located in the glove compartment (easy to run wires through the firewall, right next to the lift pump relay and 12V and ground posts). It is a 3-position (on/off/on) swtich with a middle terminal (for source) and the two side posts for which circuit you wish to use. I had GREAT difficulty trying to wire this with the positive circuits. Final solution: diesel lift pump remains positive wired to the relay. Safety features etc etc OPS all that stuff. Veg lift pump (mounted on the back of the mounting bracket I fabricated for the veg filter) is wired DIRECTLY to always on 12V source. The middle post on my switch is wired to a good ground (there's on to the left of the lift pump relay, next to all those 12V posts), and one side post supplies ground to the diesel lift pump (all the way down on the frame rail, just run the wire all the way down there and solder, tape and seal it VERY well) and the other side post supplies ground to the veg pump. If you turn the truck off in diesel mode ... YOU'LL KNOW! The pump will buzz at you, even after you've pulled the keys out. This is a GREAT alarm system, it's already reminded me once to turn the truck back on and purge the system. When the switch is in the diesel position, the pump will obviously turn off when you turn off the ignition, because it's wired through the relay. I don't really need the off position.

Diesel operation: switch is in diesel position, 3-way valve is returned to diesel tank. Turn on truck, drive until you're sick of using diesel.

Switch to veg: flip the lift pump switch. You're running on VEG! Don't forget to switch the 3-way valve so it will loop back, instead of dumping veg into your diesel tank.

Purge: flip the switch back. Wait. I have a ball valve in my system, which I though was necessary to purge the system. I *think* that the positive pressure given by the diesel lift pump at this point will NOT allow fuel to loop from the veg line and into the T.
centralvalleybiodiesel CF
1993 GMC Sierra K2500 6.5L + homebuilt veg kit, OEM glowplug failure (update: rebuilt with a 6.2 block, working fine)
1988 Ford 6.9L OEM dual tank, 90+% veg oil blend.
1989 Ford 7.3L, 80+% veg oil blend.
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Location: Pembine, WI

Dodge or GMC

Postby gandjwhite » Sat Apr 05, 2008 8:55 pm

I'm assuming you have the Duramax engine with the Allison Transmission?

I've seen where that is in stiff competition with the exceedingly awesome Dodge Cummins engine (which comes with a crappy truck with a bad transmission).

I can't decide which I should get. I believe the GMC would be cheaper but I'm not sure the engine is as reliable as the Cummins.

How much did it cost you to convert yours to WVO?
How long before you can get some pics up?

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Joined: Fri Apr 04, 2008 5:17 pm
Location: Sonora, CA

Postby SunWizard » Sat Apr 05, 2008 9:18 pm

The duramax was not until 2000, and is far better than the old GMs. The >2000 GMs won't be cheaper than the dodge cummins, they are about the same $ for similar mileage and condition.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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