I've been lugging around a NWMP fuel tank for the last 14 months and I finally got tired of moving it around to different locations, so I decided to finally install it today. It's supposed to be a gravity feed system with a hose running into a fitting where the main tank drain plug is on the bottom. Problem with this is I don't like the idea of having something hang even lower off the main tank, especially a brass fitting that could drain all my fuel if it gets hit hard enough.
So I thought of putting a shut valve on it (elec or manual) and have the aux tank drain into the filler neck vent tube for the main tank, but the filler neck is too high and I don't want to put a hole lower than that in the side of the main tank because I'm afraid it'll leak.
My final option is an electric fuel pump, but fuel pumps can get damaged when they run dry from heat build up and I would have no way of knowing when to shut off the extra pump. I can't find anything saying they are safe for short periods of dry running and likewise nothing about how they work except that they do not use a diaphragm.
This is what I came up with, though it may be a bit over engineered it should save the pump from running dry, and if the rest of the system wiring fails a jumper wire across the load side of the relay will still turn on the fuel pump
Red: fuel lines
Dk Blue: wiring
Parts: low pressure nitrous fuel safety switch (adjustable 2-5psi), fuel pump, momentary & toggle switches, relay, slight fuel line restriction (small crimp in steel fuel line to main tank)
- the toggle switch turns on the system, but the relay won't turn on the fuel pump until there is ~3psi at the low pressure switch
- press the momentary switch to bypass the pressure switch and turn on the relay and fuel pump
- pressure builds behind the restriction and makes the pressure switch close, the momentary switch can be let go now as the relay will stay on
- when the aux tank runs dry the pressure switch opens deactivating the relay and fuel pump
if I really want to get fancy, I was thinking I could run a wire from the + side of the fuel pump back up to the switch panel through an LED and on to ground as a "fuel pump on" indicator light
Installing the tank is easy, so I'll leave out the bits about drilling holes and bolting it into place. It's the details that'll make it trouble free in the long run . . . like an exhaust heat shield so the gas doesn't start get too hot (excessive vapor/boiling)
view from the wheel well - before I fill it for the first time I'd like to replace the rubber hose with steel braided to help deter thieves from thinking it would be easy to cut the rubber hose and steal my gas - I was also thinking a steel hard line would work, but I'd have to find another fitting first
transfer pump (universal, for a carb'd car) - I used 1/4 riv-nuts to attach it to the frame rail (still need to put a fuel filter inline to pretect the pump)
a bit of protection to keep the hoses from chaffing against the frame rail, it also keeps them tied together nicely so they don't move around much
a few months ago I had to repair the main tank fuel pump bracket because the metal line on the outside finally rusted through, while I was at it I added an extra line to dump the fuel from the aux tank into the main tank, I had actually extended that fitting down to the bottom of the tank in the hopes that it would work like a siphon once fuel starts flowing (in case the pump fails/doesn't work out I could still use the aux tank w/ pump removed)
I tossed my spare tire back under there and noticed that the tank didn't affect my departure angle at all, though if I drop off an obstacle the spare will definately take the drop. If I know I'm hitting any rough trails I'll just take the spare off and toss it in the back. I am planning on making some kind of spare carrier for the rear bumper - I always liked the idea of being able to carry 2 spare tires for longer trips.
rear view
I still have to wire it up, but that'll have to wait for another day . . . the wife started giving me the hairy eyeball for working on the truck most of the day.
So I thought of putting a shut valve on it (elec or manual) and have the aux tank drain into the filler neck vent tube for the main tank, but the filler neck is too high and I don't want to put a hole lower than that in the side of the main tank because I'm afraid it'll leak.
My final option is an electric fuel pump, but fuel pumps can get damaged when they run dry from heat build up and I would have no way of knowing when to shut off the extra pump. I can't find anything saying they are safe for short periods of dry running and likewise nothing about how they work except that they do not use a diaphragm.
This is what I came up with, though it may be a bit over engineered it should save the pump from running dry, and if the rest of the system wiring fails a jumper wire across the load side of the relay will still turn on the fuel pump
Red: fuel lines
Dk Blue: wiring
Parts: low pressure nitrous fuel safety switch (adjustable 2-5psi), fuel pump, momentary & toggle switches, relay, slight fuel line restriction (small crimp in steel fuel line to main tank)
- the toggle switch turns on the system, but the relay won't turn on the fuel pump until there is ~3psi at the low pressure switch
- press the momentary switch to bypass the pressure switch and turn on the relay and fuel pump
- pressure builds behind the restriction and makes the pressure switch close, the momentary switch can be let go now as the relay will stay on
- when the aux tank runs dry the pressure switch opens deactivating the relay and fuel pump
if I really want to get fancy, I was thinking I could run a wire from the + side of the fuel pump back up to the switch panel through an LED and on to ground as a "fuel pump on" indicator light
Installing the tank is easy, so I'll leave out the bits about drilling holes and bolting it into place. It's the details that'll make it trouble free in the long run . . . like an exhaust heat shield so the gas doesn't start get too hot (excessive vapor/boiling)
view from the wheel well - before I fill it for the first time I'd like to replace the rubber hose with steel braided to help deter thieves from thinking it would be easy to cut the rubber hose and steal my gas - I was also thinking a steel hard line would work, but I'd have to find another fitting first
transfer pump (universal, for a carb'd car) - I used 1/4 riv-nuts to attach it to the frame rail (still need to put a fuel filter inline to pretect the pump)
a bit of protection to keep the hoses from chaffing against the frame rail, it also keeps them tied together nicely so they don't move around much
a few months ago I had to repair the main tank fuel pump bracket because the metal line on the outside finally rusted through, while I was at it I added an extra line to dump the fuel from the aux tank into the main tank, I had actually extended that fitting down to the bottom of the tank in the hopes that it would work like a siphon once fuel starts flowing (in case the pump fails/doesn't work out I could still use the aux tank w/ pump removed)
I tossed my spare tire back under there and noticed that the tank didn't affect my departure angle at all, though if I drop off an obstacle the spare will definately take the drop. If I know I'm hitting any rough trails I'll just take the spare off and toss it in the back. I am planning on making some kind of spare carrier for the rear bumper - I always liked the idea of being able to carry 2 spare tires for longer trips.
rear view
I still have to wire it up, but that'll have to wait for another day . . . the wife started giving me the hairy eyeball for working on the truck most of the day.
rolleyes
Got a protractor handy, take a full shot so i can get both wheels as the base b/c I'd like to see if it's around 40 or so. 