I believe it draws about 5-7 amps when pumping ~4-8 psi to an Edelbrock carb. I also understand that electrical relays are needed for loads greater than ~15 amps (e.g. electric fans, halogen lights, etc), assuming standard gauge wires and switches. Anything less than that can be wired directly through the ignition switch. Based on those facts, it seems a relay adds unnecessary complexity for my application. What am I missing? Thanks, guys.
If it's only drawing that many amps I'd just put a fuse in the hot wire and be done. I grew up before everybody went to using relays on things like electric fuel pumps etc. I'm amazed on some cars that I've seen wired that even have relays on low draw circuits.... ...
I put one in for mine. I made it as bullet proof as possible. I also run a pre filter before the pump
I run the 4070 on pretty much everything I have and have typically not used a relay, and also usually run power to it through a basic toggle switch. Tens of thousands of miles, I've never had a problem. Make sure you use the terminal retaining clip or some other means to keep the hot and ground on, they will fall off in time if you don't.
I didn't use one on the very same pump. I do wish I would have put a switch in line though, sometimes I needed the key to be on to troubleshoot wiring things and the pump would just run, I'd have to find the terminal on the panel and unplug it.
That's exactly the reason why I put the pump on a toggle. Sometimes I just need the key hot and I don't need the pump running continuously. I had considered the oil pressure switch like Jim mentioned but my Olds engines don't have the oil pressure that Chevys and Ford have, so having the pump run at initial start up is great since the engine has instant fuel pressure. It eliminates that long crank.
Right, here in Texas fuel evaporates from the bowls in the heat so fast that it's nice to let the pump fill them before cranking. I learned my lesson and put a switch on the pump for a hot rod VW bug I built. It was also make-shift anti-theft, and If I knew I wasn't going to drive it a while I'd shut the pump off and let it run out of gas so the crappy ethanol wouldn't evaporate and leave gunk in my finicky Weber carbs.
Need to add altogether all amp pull on ignition switch On with length of wire & that is a Good Quality switch I like to have control of pump No mater key on or off , I do not like wired to oil switch just in case it goes bad , Over years I add relays on all combined separate circuits, on high amp pulls I run the Freightliner style relays with 1/4 connections, 60,70,80 AStory on separate switch for fuel pump, Back in late 70 my uncles 67 SS II was stolen 2 time , it was found less then 1/4 mile away because of hidden & separate power supply to the electric pump.
I like relays for all electric fuel pumps. Plus, when I wire them up i wire the ground on the relay through a switch so that I can disable the relay when working on something or when I park it as an anti-theft device.
I used one with my electric fuel pump mostly because I have too much other stuff wired to my ignition switch and didn't want to stress it any further.
With me it goes back to 19Eddy30 said, in that relay/no relay all relates to the TOTAL amp load on the ignition switch. Personally I have come to prefer relays to lighten the load on the switch and run any and all accessories through the fuse block rather than straight to the switch. I agree 100 % that one should include a separate switch to be able to shut the electric fuel pump off though. I found that out on my 57 Chevy panel back in the 70's when that was my introduction to electric fuel pumps.
If you decide to run without a relay, don't cheap out on the toggle switch. Years ago a friend had a cheap toggle switch melt (powering his fuel pump). I ran without a relay and bought a quality toggle and never had an issue. Also, I put my fuse in my trunk (inline) ... made for a great anti-theft device.
I've never used a relay for an electric pump, and I've been using them since the sixties with no problems. I do use a toggle switch so I can turn it off if I need the key on for any reason without the pump running.
I've just used a normal toggle switch in the past, with no problems. This time around I decided to use a relay. It's powered through an oil pressure switch on the engine. Also have a bypass switch on the dash...and a super duper secret switch that kills power to the pump
Good thing we have the HAMB to relay relay information. No really, I mean relay, no scratch that. Really. Here's the thing, I get where some things benefit, but now EVERYTHING has to be relayed or else Not long ago we were reading about a main relay to operate the beloved jerk off switch (master shut off for the non-drag racers among us). How many load wires can feed that battalion of relays up under the dash panel laid out in a fashion that even makes the billet crowd swoon, huh? Shortest wires of the right gage, fuses as appropriate, and a little bit of proper research as to load requirements by asking the right questions of that super computer in your hand rt now. I coulda said it a lot shorter. Fuck that relay, don't need it.
New cars are full of relays. Used to be we just needed one for the horn, because the horn switch was grounded (not for the current it draws) if you're building a traditional car, you don't need a relay for everything.
I use the 4070 for cold starts, to prime the carb. I have a manual switch. It runs fine with a ten Amp fuse and no relay. I have an inline pre-filter. When driving I usually run on only the mechanical fuel pump.
Well, I use a toggle switch for the pump and fuse and a relay. It is up to you my buddy. It is personal preference I think. If it works ,it works.
Oh, and by the way, I have the Carter race pump, electric. I forget the part #, I'm getting old, I turned 61 today.
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