Hello. I have a holley red fuel pump and I need help wiring it. I have an aftermarket 12 circuit wiring kit. I didn't use the electric fan cable,radio or power antenna. Can I use any of the these to power the pump? I ordered a holley regulator also.. I think the fan is wiring to a relay so I'm hoping that when I turn the switch,the pump turns on to supply engine. Thaks in advance
If there is a fan relay wired up in the harness already, that should work for the fuel pump. The fuse size might be higher amps than you need for the wire size that you would run to an electric fuel pump. The pump should only draw about 5 amps, so a 10 or 20 amp fuse will be sufficient, and you can use 14 or 12 gauge wire to the pump. Electric fans usually draw 30 amps or so, and require 10 gauge wire.
You might want to look into some type of safety switch in case of accident. A means to automatically shut off the fuel pump, like loss of oil pressure.
I will look into it.. Thanks @squirrel,so If I wire the pump to the fan wire I don't have to wire a any other switch right?
You do want to check switch load upstream from the loads, i.e. make sure maximum current doesn't exceed the switch rating. Electric motors have two current ratings you need to be aware of; running current, which is the spec usually given, and inrush current when starting. 'Instantaneous' inrush current can be up to 1200% of running current, but using a 300% figure when sizing wire/fuses/switches will generally give you adequate 'headroom' in the circuit for safe, reliable operation. Basically what that means is if you're using a relay to power the motor, it's main power feed for the motor should NOT go through the ignition switch, only the light-load relay coil that operates the relay should be powered through the switch.
I don't know how the wiring harness you have is wired up, I can only guess at the answer to that. You'd need to show us the instructions for the harness, or something, so we could help you figure it out.
I added a switch override on the dash next to the ignition key to shut off the pump. It has come in handy to run the carbs dry for servicing.
The fan circuit in your harness may be "always on," allowing for the fan to be thermostatically turned on and off even if the key is off (this is standard practice in modern cars... if your wiring harness does this too, your pump will run when the key is off = very bad). Use the radio circuit instead. That is certainly good for the 5 amps or so your fuel pump will use. No need to make it more complex with a relay. You just don't need the extra juice. Radio circuit will be key-on (not to be confused with radio "memory" circuit, which is always on). A manual kill can be wired inline... again, fuel pumps don't draw much current. Any decent, well made "automotive" toggle will handle the current.
Sorry, but not a good idea. The radio circuit will be controlled by the ignition switch, and while the pump may pull only 5 amps once running, the inrush current (which will be at least double, more likely triple) may (depending on what other loads the switch sees) exceed the switch amp rating and shorten it's life. If the fan circuit is 'always on', use that but install a relay to feed the pump. You can then use a switched circuit to operate the relay coil, adding only a minimal load to the switch.
Sorry, but not correct. While we still don't know from OP what wiring harness product he's using, NONE of them worth a dime would actually pull current through the key. The key simply energizes the "key-on" rail in a fuse panel. If it didn't, that would mean EVERY key-on circuit would be pulling current through the key. That would be the worst designed product in human history. As for inrush current, that WAS the 5 amps being bandied about. Per Holley, operational current is 2A. A typical car stereo "25 watt in dash AM/FM/CD" type unit draws 2-3A continuous. The radio circuit is plenty for the fuel pump. I have no idea what this means? What else might one be planning to wire to a "fuel pump on/off switch"... and why? Also, this $3 generic toggle switch, which is very representative is rated to 15A. Edit to add this finger painting I just knocked out. Battery+ feeds entire fuse panel, switched side (orange) is only energized when key (green) flips the relay... but the actual juice for the switched side of the panel is provided entirely by B+ circuit. NOTHING through the key itself. The key provides the 10mA (that's a mere 0.01A) to trigger the coil. That's it.
For an electric fuel pump it would be better to run a separate harness and relay kit: https://www.ebay.com/itm/Mr-Gasket-...roAAOSwwZVcPRoI:sc:USPSFirstCl***!85037!US!-1 The wiring from the relay back to the pump should be 10 gauge. The diagram is here: https://www.carid.com/images/mr-gasket/fuel-systems/pdf/40h-installation-instructions.pdf
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