Fuel Pump Cutoff For Carbs Options

[Spoke]

I'm preparing to install a 2056 dual Weber carb engine in my car and was thinking about how to control the fuel pump. I'll use the existing FI fuel pump relay as done many times before by grounding the appropriate pin on the FI ECU connector to energize the relay with ignition on.

I want to add a safety feature to power the fuel pump only when the engine is running. This is done with all FI systems in case of accident so the fuel pump doesn't keep pumping if the engine has stopped. I want the same functionality with carbs.

I'm designing a PCB to power the fuel pump like DJET systems do: Turn the key on and the fuel pump charges the system for 2 seconds then turns off. When the engine starts turning, the fuel pump will run.

I forsee 4 wires:
GND: picked up on a chassis lug near the relay board
12V switched: Picked up on the FI ECU socket
Relay: Picket up on the FI ECU socket
Coil Neg: This goes to the tach as well.

The coil negative would be the signal to indicate engine running.

Should I consider any other functionality of the fuel pump controller? Anyone interested in a PCB like this?

Does a 2 second precharge do anything for a carbed engine? I could see if the carb bowls were not full but other than that, not sure a precharge does anything.

[JFJ914]

And still, my single relay circuit does the same job but its much simpler.

(IMG:style_emoticons/default/agree.gif)

I can't see why all this work? (IMG:style_emoticons/default/confused24.gif)
Is it just to keep the relay on the board? (IMG:style_emoticons/default/wacko.gif)
Again why? It's carbed so it's not like it's concours. (IMG:style_emoticons/default/poke.gif)

The relay Valy posted works on oil pressure, the the relay I posted uses a simple tach input, both could be quickly stealth installed without a single OEM wire cut...so I don't get it?

Sometimes the challenge of reinventing the wheel proves irresistible!

[Spoke]

And still, my single relay circuit does the same job but its much simpler.

(IMG:style_emoticons/default/agree.gif)

I can't see why all this work? (IMG:style_emoticons/default/confused24.gif)

Keep in mind that I am an engineer and it's the engineers code to solve any problem in a manor such that the problem didn't need to be solved in the first place and to make the solution so complicated that no one can figure it out.

(IMG:style_emoticons/default/beerchug.gif)

Is it just to keep the relay on the board? (IMG:style_emoticons/default/wacko.gif)

Yes the relay is already there and want to provide the bit of protection that shuts the pump off when the engine stops. I want to be able to switch from carbs to FI easily. This circuit will mount in the FI power connector on the relay board with one wire going to chassis and the other to the coil.

Again why? It's carbed so it's not like it's concours. (IMG:style_emoticons/default/poke.gif)

Just having fun with electronics.

The relay Valy posted works on oil pressure, the the relay I posted uses a simple tach input, both could be quickly stealth installed without a single OEM wire cut...so I don't get it?

Again, fun with electronics. Here's a board I just finished for my 3d printer. It is an LED ring that will fit right inside the carrier to illuminate the work. Could have bought a generic LED ring for $30 but this one is more intricate and fits beautifully on the printer. Theirs has 6 LEDs and mine has 8 LEDs so mine is better.

[Valy]

You're not true to your signature: "CSOB of PA"
(IMG:style_emoticons/default/smile.gif)

[euro911]

... Keep in mind that I am an engineer and it's the engineers code to solve any problem in a manor such that the problem didn't need to be solved in the first place and to make the solution so complicated that no one can figure it out.

(IMG:style_emoticons/default/beerchug.gif)

(IMG:style_emoticons/default/laugh.gif) I remember designing similar elaborate circuitry, but then I had to write documentation so our field engineers had a road map for troubleshooting. Then I had to write additional documentation allowing normal folks to operate the device(s).

Glad I'm retired now (IMG:style_emoticons/default/aktion035.gif)

[Spoke]

Here's a first cut at the PCB and the FI plug. I can shrink the board a bit. Right now the entire assembly is a bit over 2 inches tall.

[Spoke]

Here's a simpler circuit which interfaces to the oil pressure switch to sense engine running. I think I'll add an LED to indicate the pump is powered.

[Spoke]

Here's the layout of the oil pressure fuel-pump cutoff. Should have the board back in 2 weeks. Shrunk the board to 0.6in x 0.7in. It's tiny.

[Spoke]

Got the boards back. Gotta order a few parts then assemble and test. As I mentioned before, they are tiny.

[euro911]

Oh, when you said they were going to be really tiny - I was thinking like, smaller than a dime (IMG:style_emoticons/default/poke.gif)

[Spoke]

Oh, when you said they were going to be really tiny - I was thinking like, smaller than a dime (IMG:style_emoticons/default/poke.gif)

The power FET and catch diode pretty much determined the size of the board. I used 0603 sized resistors which are best soldered when using a microscope.

(IMG:style_emoticons/default/beerchug.gif)

[Spoke]

You're not true to your signature: "CSOB of PA"
(IMG:style_emoticons/default/smile.gif)

Well we'll see how much this adventure costs. I like to stay true to form.

I've already got $2.10 invested for the PCB alone; That's for 3 PCBs; Including shipping.

[Harpo]

Very nice there Jerry. I would be interested in one of these if you decide to sell them

Thanks

David

[andys]

http://www.summitracing.com/parts/sum-890145
This is what I used on my six conversion. Easy wiring and installation.

That's a Ford inertia switch. I installed one on my LS1 conversion car. Make sure it's readily accessible in case you get bumped. Ford placed them in all sorts of weird places that were difficult to get to. On my Explorer, it was high up under the right side dash, on the Supercoupe, it was in the trunk.

Andys

[porschetub]

And still, my single relay circuit does the same job but its much simpler.

(IMG:style_emoticons/default/agree.gif)

I can't see why all this work? (IMG:style_emoticons/default/confused24.gif)
Is it just to keep the relay on the board? (IMG:style_emoticons/default/wacko.gif)
Again why? It's carbed so it's not like it's concours. (IMG:style_emoticons/default/poke.gif)

The relay Valy posted works on oil pressure, the the relay I posted uses a simple tach input, both could be quickly stealth installed without a single OEM wire cut...so I don't get it?

the whole thing has got very complicated and don't really see the point of making it to hard,bypass wired is the known method from FI to carb works is good enough,if you crash and we do ,you turn the key off......simple really.
We are looking @ a low pressure supply afterall not a biggie,cheers.

[mepstein]

BJ's 6 conversion caught fire when the fuel pump kept running after he turned off the key. Better safe than sorry.

[SKL1]

Got the Ford inertia switches for both my cars- installed one on the '73- didn't any instructions but luckily mounted it button up as I now see on their catalog page.

If you got that route, definitely get the wiring plug as it makes installation a snap.

Can kind of use as a theft device but pushing the button in to turn off power to the pump.

[Spoke]

Sometimes the challenge of reinventing the wheel proves irresistible!

(IMG:style_emoticons/default/agree.gif)

Never be complacent with what is available. I enjoy the challenge of designing and building things.

Why buy these for $5 total...



When I can buy this for $35 and have some real fun...