Electric Fuel Pump - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

 
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post #1 of 13 (permalink) Old Oct 8th, 03, 05:01 AM Thread Starter
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I have an in tank walbro pump that I need to wire up(for my potential EFI conversion). From the spec sheets I have seen that it draws 5-7 amps. I will have to run a wire to supply power from the firewall(or so) back to the pump. What gauge wire should I run considering that it must be about a ten foot run? Actually how do you figure the gauge size based on amp draw and length of wire?

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post #2 of 13 (permalink) Old Oct 8th, 03, 06:18 AM Thread Starter
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I just thought of another question.....

If I am running an electric fuel pump with a carb and no ECM, how can I wire a switch or something to turn off the fuel pump when the engine is not running and the key is on? For example....I get into an accident and a fuel line is ruptured, the key is on and I am dazed and can't turn the key off. The fuel pump keeps running pumping fuel out of the ruptured fuel line and then we have a 69 camaro ragtop/paulm barbueque!!!


Hey I was thinking.....My electrical oil pressre sender makes 240 ohms of resistance at zero oil pressure.....What kind of a switch could I make that would turn on or off based on the resistance given by the sender?


Ooooooh, wait.....My Low fuel light is something like that....When the tank sender hits a certain resistance it turns on the light!!!

[ 10-08-2003, 02:35 PM: Message edited by: paulm ]

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post #3 of 13 (permalink) Old Oct 8th, 03, 10:28 AM
 
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You need to add a oil pressure safety switch. This is a switch which will turn off the electric fuel pump when the oil pressure drops below a set pressure. Like when the engine dies in an accident so the fuel pump does not keep pumping gas onto an open flame. I know Holley sells this I am sure there are many others.
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post #4 of 13 (permalink) Old Oct 8th, 03, 10:31 AM Thread Starter
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I saw the Holley oil pressure switch. I already have the sender for the oil pressure gauge in that hole. I'm not sure that I can fit two senders back there....

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post #5 of 13 (permalink) Old Oct 10th, 03, 05:53 AM
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Just a note, if you were to wire your fuel pump cutoff to your oil pressure switch (or a similar) switch/sending unit. How would you get your car started? You won't have any fuel pressure, because the pump will be off until you have oil pressure, you won't have oil pressure until the car starts. Does this make sense? That just crossed my mind, I haven't thought of a way around it yet (I'm sure it wouldn't be difficult to make it happen).

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post #6 of 13 (permalink) Old Oct 10th, 03, 06:16 AM Thread Starter
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You would have to wire/build the cricuit so that the switch would be overridden/energized by the starter. So really there would be two "ON" switches.....One from the starter and one from the oil pressure, either could activate the switch.

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post #7 of 13 (permalink) Old Oct 10th, 03, 07:45 PM
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Yes that would work. Like I said I was just reading your post and thought, there could be a slight problem. You got it figured out, just wanted to make sure you thought of that.

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post #8 of 13 (permalink) Old Oct 11th, 03, 07:34 AM Thread Starter
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In theory, yes I think that I have it figured out. In application, I'm not sure how I will construct it!!

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post #9 of 13 (permalink) Old Oct 12th, 03, 08:20 AM
 
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Oil Pressure Safety Switch
It's always a good idea to place a safety switch in the circuit when installing an electric fuel pump. Holley has one available under P/N 12-810. This switch will ensure that the electric pump will not work unless the engine has oil pressure. It will prevent the pump from running in a situation where the motor may stall with the ignition ON. Wiring the switch through the starter solenoid circuit energizes the pump on engine start-up. After the engine is running the switch continues to provide power to the pump as long as there is oil pressure to keep the switch turned on. There is enough residual fuel in the float-bowl or fuel line to start engine, until oil pressure builds up and energizes the electric fuel pump. I have used one for about a year. No Car-B-Q for me. I would not run a electric fuel pump without one.
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post #10 of 13 (permalink) Old Oct 12th, 03, 01:03 PM Thread Starter
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Yes, I am aware of the Holley part. The problem is that I don't think that I have enough room for the electrical oil pressure sender for my gauge and the holley switch.

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post #11 of 13 (permalink) Old Oct 13th, 03, 08:54 AM
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Actually the factory oil pressure switch is in parallel with the fuel pump relay. If there is a fluctuation in the voltage, the relay drops out or goes bad, the fuel pump will remain on as long as there is oil pressure. there is an inertia switch that they have to shut the pump off. I got mine from a Ford because its small and simple. it goes in series with the pump wire. if theres an accident you have to push a button on the inertia switch to get the pump to run again.

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post #12 of 13 (permalink) Old Oct 13th, 03, 11:06 AM
 
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I hope I am not beating the dead horse here? Is it possible to install a tee so you can use your electric sending unit for oil pressure gauge and add switch to tee. This is what I did, but I have mechanical gauge. Not sure how big a electrical sending unit is?
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post #13 of 13 (permalink) Old Oct 13th, 03, 12:12 PM Thread Starter
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The electrical sender is about the size of a dixie cup. It was already tight just getting the sender in there....That's why I was thinking of building a circuit/switch to run of the resistance from the sender.

[ 10-13-2003, 04:47 PM: Message edited by: paulm ]

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