Project - New Fuel System

[aston]

Well, I finally decided to rework my fuel system. The problem was when the system got very hot (105 ambient, 120 fuel) the fuel pressure would just go away and the pump would howl.

My original scheme was designed to fit under the floor, ahead of the rear axle in the space bounded by the frame rails, the cross member and the floor. I selected an RCI tank that fitted almost perfectly: 17 x 30 x 7.



This tank has a large area but is very shallow: not good for scavenging fuel at extreme angles. I designed a dual pick up system that would slide forwards and backwards and had valves that would close when they tried to draw air. It worked superbly: I could continue to pull fuel with very little in the tank at crazy angles.



Now back to the problem: getting stuck in the heat.

The (slight) restriction provided by the pickups coupled with the high fuel temperature caused the pump to cavitate. No pressure, lots of noise = stuck.

There was a secondary problem of the shocks hitting the tank but this only happened in extreme circumstances and did not appear to be doing any permanent damage, but I wanted to correct it all the same.

The root cause was the shape of the tank. The simple answer was to just mount a big honking tank in the back where the rear seat used to be.

This was vetoed by the dog.



More to come!!

[sarah]

You have a very clean garage!

[blkTJ]

Hey now!!! :yay:

[Mtbikbob]

I see the dog, made his point.... now thats funny.

[aston]

Next thrilling installment

I needed a tank with a better shape. It had to be deep enough to allow the fuel to be scavenged by the pump without an elaborate pick up, but not take up so much room that the dog is pissed off.

I spoke to the folks at fuelsafe.com and they suggested I consider a collector. A collector is a tank within the tank that has an ideal shape for fuel pick up. The collector is supplied with fuel from the main tank, making use of the fact that the fuel sloshes around. Given the fact that we spend so much time at odd angles, I wanted to make sure the fuel would slosh into the collector even when the actual fuel level was getting low. So, I shaped the underside of the tank to direct the fuel to the center/rear where the collector would be mounted.

I also wanted to trim the sides a little to clear the shocks and all that…so here’s how it looked in theory….









Looks good, eh :homer:

[sarah]

I don't get it, but the geek appeal is first rate!
Woot!!! (We love our geeks here at mjr) hehe

[USMC 0369]

Not to be a Geek... I really have no idea what I'm doing on this damn electric box sometimes. But I'm trying to get Aston's design idea. I'm no engineer (by a LOOOOOOOONG shot), but I'm wondering how your going to get fuel to the pick-up inside the box once the fuel level drops below the top lip of it.

If the fuel is above the lip (greenish color) then no problem, I gotcha. But when it's below (blue-ish color) I'm wondering? I see how it would hold fuel in for the pick-up to function, but how do you get the fuel in there in the first place? Or is it a matter of mashing on the brakes at stoplights if you're not off-camber...



Everyone knows my avatar is speaking directly to me anyway.

[aston]

...how do you get the fuel in there in the first place?


Excellent question, I'm glad someone is paying attention

The collector has one-way ball valves that allow the fuel in, as it sloshes around the tank, but it gets trapped and keeps a constant supply of fuel to the pump. There is now no need for any pick-up plumbing, the pump is simply suspended in the collector with the inlet close to the bottom.

Here's the tank...



Here's the collector from the top



Here's the collector from inside..



The ball valves are covered with tape to keep shite out while drilling, cutting and grinding!

[USMC 0369]

Aaaaah now I see.

You never mentioned you had balls before!

:haha:

[YJwonderboy]

That's a sexy tank!How many gallons is it?

[Dukes69]

does it hold pressure?

[aston]

That's a sexy tank!How many gallons is it?

19 gallons (US)

[aston]

does it hold pressure?

Of course not :homer:

I made a u tube manometer to accurately measure 3 psi. At first it leaked but after a little tweaking it was toight as a toiger.

[mpc]

Interesting build. I'm thinking about switching to a similar shape tank (RCI 17 gal), but I'm a little concerned about the shallowness of it as well. For the way I would mount it in my Jeep (length wise), the pick up would be towards the rear, which would work well for going up hill. I guess if I just don't let the gas level get too low, the pick up wouldn't be a problem.

Anything wrong with just making it a sump outlet?

[aston]

Interesting build. I'm thinking about switching to a similar shape tank (RCI 17 gal), but I'm a little concerned about the shallowness of it as well. For the way I would mount it in my Jeep (length wise), the pick up would be towards the rear, which would work well for going up hill. I guess if I just don't let the gas level get too low, the pick up wouldn't be a problem.

Anything wrong with just making it a sump outlet?

What is the max downward angle that the pick-up can tolerate with half a tank of fuel, what about 1/4 tank? Assuming the tank is 7x17x30 (17gal)

If I might answer my own question In the case of 1/2 tank, if the pick-up was located exactly in the lower rear corner, the answer would be arctan 7/17 or 22 degrees. 1/4 tank would be arctan 7/4*2/17 or only 11 degrees :-( :geek:

Not enough, in my opinion.

Can you describe a sump outlet?