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Just about got the Miata body stripped, but I've not located the fuel pump - I must have unhooked the electrical connection somewhere, but I've not found the pump - do I need it for the final build, or will the tank I order have a more compatible pump?

Steve

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The pump is part of the fuel level float assembly, located on top of the tank and accessed within the car.

You could use an 80s ford ranger/bronco II pump with a typical gravity fed tank. It is frame rail mounted/isolated in a metal cage. These vehicles have a low pressure pump within the tank to lift the fuel to feed the frame rail mounted high pressure pump. It is cheaper to buy a used assembly for the pump bracket and hardware, then buy a new pump for about $50. The pump with a new bracket is closer to $180. The pump uses ford slip-on plastic fuel line connections but the fittings can be swapped for standard barbs.

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I'm still a bit confused - do you think it's worth trying to extract the fuel pump?
Or is buying a new one the best way to go?

Steve

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I bought mine from Summit for $60. It works great, but is very loud. You wouldn't think fuel pump noise would be a problem, but it's annoying. Much better since I isolated it with 1/2" of dense foam, but still noisy.

Doing it again, I would find a way to put the fuel pump inside the tank, like the Miata. That might be with the Miata pump, or aftermarket. Shouldn't be hard to pull off, either way. I think Rusty did that on his.

I'd recommend you pull the Miata pump and study it. I think you'll find a good way to mount it in the tank. Then tell us how.

I don't think you'll have much luck using an internal pump outside the tank.

-dave

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Can't use an internal pump outside the tank... for long anyhow. It relies on the fuel to help cool it. It'll burn up in short order.

Ask me how I know!

If your going FI, you can find any of the early model VW (78-99) and borrow one of their pumps. They will shoot fuel about 50ft and they are very quiet for as powerful as they are. We used the CIS pumps (78-89) when we did our Megasquirt conversion and they were perfect. Tons of pressure and volume... especially important when uprating injectors!! PLUS.. they come in a nice foam housing wich is perfect for exposed installs like a Locost!

Good Luck!

KS

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+1 each for MiataV8 and dhempy's comments. The external high pressure pump is the standard for Miata Locosts to date, but somebody's going to come up with a way to use the nice quiet (and absolutely free) stock pump (and fuel gauge sender) and the world will be a better place. Chet's (and then mine) Locost had the fuel pump behind the driver and it was so loud that once when I was cruising real slow, a spectator on the street asked me if it was an electric car. I'm not making that up.

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I don't understand, what the issue with using the stock pump?

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I can explain it to you,
but I can't understand it for you.

Ya know, I've always understood that to be the case, but now that I think about it, I'm confused. It makes sense when the pump is submersed, but that's not always the case. For the last 1/4 - 1/2 (?) tank, the pump is emerging from the fuel. For the last gallon or two (guessing), only the sock and pickup are wet...the pump is entirely up in the air, in a sealed cavity, presumably heating that cavity up. I'm guessing you could run like that for 10 to 40 minutes, easy, and that's after an hour of semi-submerged running.

Am I off-base? Maybe I'm not remembering the shape of the tank correctly. (it is a funny shape) Does the pump stay submersed in a well until the last pint or something?

I still don't think taking an internal pump out of the tank is a good idea. If nothing else, I suspect the input end is not set up to receive the plumbing.

-dave

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...nowadays people are so intellectually lazy and lethargic that they can't build ANYTHING with their hands. They'll spend hours watching whiny people marooned on an island, but won't spend a second adding anything to the world. -weconway
Visit my [Locost 7 build log]

I'm unfamiliar with the miata pump and am curious about this as well.

From pictures of the pump assembly it doesn't look like it should be a problem.
I got the stock internal pump from my rx8 donor inside a tank with no problems, and that had a great big self sumping/pressure regulating/siphoning rig around it.

RX7 pump and float installed in a std book-type tank. I added a sump to match the length of the pump assy. I had to raise the EMPTY position of the float by bending the float wire a bit. I don't know how similar the Miata setup is to the RX7.

There should be no reason you can't use the Miata pump assy. It helps to keep the project Low Cost

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Wow this is turning in to quite a topic...

OK, so my first <noob> question is, if the pump is *inside* the tank - how do I get it out? - surely the tank is welded shut...

I have the FSM but it's not the easiest thing in the world to follow...

UPDATE: Just found this...

http://forum.miata.net/vb/showthread.php?t=384254

Some good pics.

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This is what I did too minus the bending of the float -- I just made my tank taller

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William Keeling
Houston Texas
Spec Miata Racer

Some (most?) internal pumps have a built-in pressure relief port that's constantly spewing fuel. Inside the tank it's not a problem, but obviously outside the tank it's a big problem. My brother's "external" pump had such a port which was impossible to tap into in order to feed it back to the tank.

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Nothing more major than putting a fuel-pump-flange sized and shaped hole in the top of your tank, and finding a way to bolt the flange to it without leaking any gas. It doesn't seem like rocket science, but it's sure not as easy as plugging in an in-line pump.

It was my understanding that the reason for spewing fuel inside the tank during operation was to have a cooling fluid (gasoline, in this case) cycling through the pump, even when the pump was exposed. The fuel cools from contact with the tank and passes through the pump again. However, "my understanding" is based on asking myself "why the heck do they do that?" and then making a guess I was happy with. I don't know if the Miata pump is a flow through fuel spewer or not.

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Locost builder and adventurer, and founder (but no longer owner) of Kinetic Vehicles

i can tell you that with gm in-tank pumps used in the 90's trucks if you consistently run the tank low then the pump heats up enough to draw excess current thru the connectors causing them to overheat and shift about then failing to make an adequate connection... but thats the only place i have personal experience

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