Fuel Pump Cutoff For Carbs |
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Fuel Pump Cutoff For Carbs |
Spoke |
Jul 13 2015, 08:57 PM
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#1
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Jerry Group: Members Posts: 6,991 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
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. |
Valy |
Jul 17 2015, 11:12 PM
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#2
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Senior Member Group: Members Posts: 1,677 Joined: 6-April 10 From: Sunnyvale, CA Member No.: 11,573 Region Association: Northern California |
And still, my single relay circuit does the same job but its much simpler.
If you insist in using a pulse detector using 555 or discreet comppnents, add an AC component to the power supply in your spice simulations, as well as a voltage increase/drop that is RPM dependent. This will make your simulations much more interesting. Your power supply doesn't seem.robust enought. Also, do you have a parasitic capacitance in the clamping diode model? Guess what that does to your circuit, especially when you have a voltage undershot from the coil. |
Mark Henry |
Jul 18 2015, 06:44 AM
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#3
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that's what I do! Group: Members Posts: 20,065 Joined: 27-December 02 From: Port Hope, Ontario Member No.: 26 Region Association: Canada |
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? |
Spoke |
Jul 18 2015, 09:54 AM
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#4
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Jerry Group: Members Posts: 6,991 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
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) QUOTE 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. QUOTE Just having fun with electronics. QUOTE 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. Attached thumbnail(s) |
euro911 |
Jul 18 2015, 11:24 PM
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#5
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Retired & living the dream. God help me if I wake up! Group: Members Posts: 8,851 Joined: 2-December 06 From: So.Cal. & No.AZ (USA) Member No.: 7,300 Region Association: Southern California |
... 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) |
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