Electric Fuel pump? Why not?

Lukas McWhorter /

So, where I work we sell a small 12V fuel pump that pushes maybe 15psi. Its designed as an inline booster pump for carbureted car motors.

I was thinking...why not use a pressure regulator, dial it back to say 5psi, bug into the headlight wire with a fused tap and see what it does?

Worth a try? Or has this been attempted and failed / succeeded before??

Re: Electric Fuel pump? Why not?

i kinda want one. my hero kit is a guzzler and i can't run a filter.

Re: Electric Fuel pump? Why not?

fuel pressure affects fuel level height in the bowl. The more fuel pressure the higher the fuel level has to be for the float to apply enough pressure to the float pin to stop the incoming fuel. To visually check fuel level height connect a clear tube to the bowl drain and raise the other end of the tube above the carb and open the fuel drain screw slightly. The fuel level in the tube is the fuel level in the bowl. Carbs meant to run on gravity feed will easily over flow with a fuel pump.

Re: Electric Fuel pump? Why not?

You can more easily run a vacuum fuel pump from the cases/intake. No draw off the stator, and it regulates fuel pressure too... (edited)

Re: Electric Fuel pump? Why not?

I'm guessing most if not all electric pumps are going to need DC, meaning they're not going to work unless you have a battery.

If you get a pump without a regulator you're probably going to have to use a smaller needle valve to keep the carb from flooding. I don't know what kind of carb you're using but I know most pumped Mikuni carbs use a 1.5 needle valve, or sometimes a 1.8 for the larger ones (40+ mm). A similar performing engine with the fuel fed by gravity needs a 3.0 or larger to keep the bowl filled.

A small Mikuni vacuum pump is going to give more than enough flow for any moped: http://www.ebay.com/itm/310408087459

Re: Electric Fuel pump? Why not?

If your fueltap is below your carb then run a fuel pump, if not then rethink your fuel supply because gravity feed seems to work well on even the largest and thirstiest motorcycles (and they run a fuel filter)

Re: Electric Fuel pump? Why not?

I bet the petcock is partially clogged if you can't use a filter.

Re: Electric Fuel pump? Why not?

Would it work for an H2o pump instead ?

Re: Electric Fuel pump? Why not?

Lukas McWhorter /

Hmm..I like the reed pump idea. I hadn't thought about that...

So, I know this is going to sound silly but whats the maximum amount of fuel and air a 50CC engine is capable of pumping? I mean obviously, the displacement is fixed but just how far can you push it?

Re: Electric Fuel pump? Why not?

pulse pumps are not self regulating. The fuel pressure they can deliver is directly dependent on the strength of the pressure pulses in which the pumping diaphragm utilizes. Running the pressure line to the intake tract, crank case or even the exhaust is a way of running the pump but all three have different strengths of pressure pulses throughout the rpm range.

The way you can regulate a pulse pump, or any pump for that matter, is to tee off the fuel line from the pump to the carb so it also dumps back into the top of your gas tank. In this way you can trick the carb into thinking that the gas tank is always topped off. It's a good way to maintain proper bowl fuel level especially if you have a very long, up and down wise, tank. 1 2

But it's not a performance increase at all, it just makes for better bowl fuel level consistency. It's mainly used if you are having trouble keeping the carb fed as the fuel level in the gas tank goes down. I run one for that reason although I claim it's to keep the bowl's fuel level the same all day long for a super consistent a/f ratio. (edited)

Re: Electric Fuel pump? Why not?

Lukas McWhorter /

Great info! Thanks!

Wait a minute.....if I remember correctly, a lot of weed eaters use a Walbro reed pump carb. It doesn't have a float or anything it just draws fuel in with vacumn and I guess it regulates depending on how much vacumn it gets.

I know some folks said that a Walbro of that style would be hard to adapt and not necessarily as well suited for a moped as the Bing float style carb it currently has, but with no float, or bowl to worry about I think it might be worth giving a try. I have read, and been told that equipment carbs are more suited to be used where it runs wide open all the time, but I mean....isn't that where you want your peak anyway on an engine that doesn't really develop power until at least 5k rpm?

Troy Bilt, Husqyvarna, and pretty much everything else uses either ZF or Walbro (ZF sucks btw, I sold power equipment for a little while) so wouldn't the carb off some industrial sized chainsaw work for this??

Its just an experimental idea, and I am open to any suggestions. If anyone has a way to possibly finagle some kind of TBI system, I'd be open to try that out to :-)

Whatever direction I go, I'll continue posting in this thread with updates. (edited)

Re: Electric Fuel pump? Why not?

yeah, I already discussed this with you.

Just get a used mikuni round slide to replace that junk bing, you'll be happy with it. (edited)

Re: Electric Fuel pump? Why not?

This talks about pulse pumps and fuel pressure and how the fuel pressure is dependent on the pulse pressure.

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