Electric fuel pump wiring?

[greenteagod]

I'm gonna snag an electric fuel pump so I can do away with the mechanical pump & regulator setup. Just read too much about those cheapie regulators blowing diaphragms and what not.

My question is, is there a certain wire I can tie in to to power this thing. I don't want to have it on and pumping just when I have the key in the first spot. I have wires going to the plug in the bumper, not sure if I should mess around with tying in to those or if I should run a new wire from somewhere in the engine bay back to the pump.

[camoit]

Use a relay. Then off the + side of the coil to energize the relay. Then the relay will send power back there from the battery. or off the ign side of the fuse box.

[pennyman1]

That is not the right place to pick up +12 v for the pump - there is a wire coming up to the factory carb that has +12 on it when the key is on - use that for the relay to power the pump. Taking it off of the ignition coil robs the coil of sufficient voltage to give max spark.

[camoit]

Whoops thats correct. I forgot he has dropping resistor. I was thinking of mine. Dhuuuuuu

[greenteagod]

Sweet, gonna be doing that this evening if I made it outside while there's still light. If not, then tomorrow!

[greenteagod]

All right, I got it hooked up, ran in to a bit of a situation though. Probably explains why my electronic choke wasn't working either. So I go to splice in to that line, hook up the relay. Nothing happens. Check the voltage on that wire, nada. So that's likely why I've had to dial my choke all the way open manually, because the electronic part wasn't working.

So that brings me to a few questions, and I'll get a picture of what I'm talking about tomorrow to further clarify things. So in installing the weber, all the wires that originally went to things, now do not. The only wire from that bundle that still goes to anything is the one for the electronic choke. I know it worked at one point because I remember it sparking when I touched the wire to it.

So first question, is there a fuse anywhere for that wire? I checked all the fuses inside the truck and all of them were good, none of them looked like they went to the choke anyway.

Second question, how much voltage does the electronic choke need? Out of that original cluster I have one 4-6 volt wire that's on when the key is fully turned, and two 12 volt wires that come on at that time as well. The others I assume are return lines as they generated no voltage and I consider them irrelevant now anyway.

Third question, since I have two 12 volt lines there that are on only when the key is fully turned, can I just use one of those to power the fuel pump and do away with the whole relay situation. It's what I did, and I just gave it a test drive, everything seemed to work fine. The pump definitely turns off when the key is in the accessory and of course off position. I don't want to screw things up though, so if there's some reason for a relay to be in place, I can hook it up.

I figure either way that most of that wire bundle is pointless now and I have a big plug and those wires that I can get rid of and just splice below the connection. Do away with the whole plug all together as I don't forsee ever switching back to the stock carb, or knowing how to even hook it up again =)

Thanks, and sorry for the long post.

[pennyman1]

The idea of using the relay is to pull power from the battery rather than the harness - I have my relay back near the pump with a 12 ga wire from the battery going to it. I also have an oil pressure safety switch installed in the block where the oil pressure sender would be that will kill the pump if the oil pressure drops to zero, but will bypass the switch when starting the motor - the schematic is on the forum for that. I have run Geronimo like that for almost 30 years with that setup - the safety switch lasted over 20 years before it finally went, shooting oil out the terminals. Put in a new one, and away I went.

[mitchugh]

I am about to go through this, hopefully this weekend. I have my weber ordered and on it's way and an electric fuel pump too. Where is the schematic located? Thanks!

[greenteagod]

No schematic really, just get a relay. Have the relay controlled by the wire for the electronic choke. And just pull power from the battery for it. That way when the key is on the relay engages and the pump is powered off the battery.

[mitchugh]

So do you not use an oil pressure switch with your set-up? I've never done a mod like this before so I'm trying to get an idea of what i need

[pennyman1]

The idea of the oil pressure safety switch is to supply power to the pump when the key is in the start position with no oil pressure and in the run position when the key is in the on position. If the motors loses oil pressure for any reason, the pump shuts off. Think of it as a single pole double throw toggle switch controlled by oil pressure instead of a lever. If you roll the truckover without the pressure switch, the electric pump keeps running.

[BradMph]

You always want to go to a BBQ, "NOT" be a BBQ! and a running pump in a crash would be a nightmare.

[greenteagod]

That is true. I should probably do that at some point =D

[mitchugh]

Ok I think I understand the relay and oil pressure switch. Definitely don't want to be spraying gas on a hot engine. I found this site and it looks like a pretty good rough guide to follow when I am ready to put in the fuel pump in.

http://www.how-to-build-hotrods.com/electric-fuel-pump.htmlhttp://www.how-to-build-hotrods.com/electric-fuel-pump.html

Is this good info to follow or is there better info out there?

[pennyman1]

use it - it works - be sure to get an adaptor for the switch to screw into the block

[BradMph]

A little example, make sure you run fuse also.
5322

[greenteagod]

Ordered myself one of those oil pressure switches. Might as well do it to it =)

[greenteagod]

So for this do you still use the original sensor as well and run a T or do you just use the new one in place of the old sensor? I tried searching for the schematic but this forum doesn't like searching three letter words, so sometimes trying to find things is a bit of a pain in the ass. Searching for switch schematic just links back to this thread right here.

Also what size adapter is needed? There are a bunch out there and I'm having trouble finding the exact spec on the original switch. Most sites are saying it's 1/8 24 npt, which that doesn't seem to be the case as that's what the new switch is and it's definitely not going in.

[greenteagod]

Found an eclipse forum where they're saying 1/8 BSPT is the thread on the block and we'd likely be going to 1/8 NPT. Fecking autometer wants $20 for their little brass widget, and ebay isn't much better. Any good sources for these?

[pennyman1]

I used an adaptor and a t to run a gauge and the oil pressure switch - napa should have them - if not I will look for them at canfield if i get there next weekend

[greenteagod]

Cool. Did you have to get another adapter for the T for the gauge light or were you going with a new switch there anyway? I've read as far as those go you can wrap it up good with some teflon tape or use some sealant for putting something that's BSPT into the NPT, but just thought I'd check.

[mitchugh]

I have a question about wiring up the fuel pump, relay, and oil pressure switch. I was looking at this diagram from above and the wire I colored red is confusing me. It looks as if this red wire is connecting power directly from the battery to the relay and then the pump. It looks to me like this set-up is by-passing the oil pressure switch, which I am not understanding. Can anyone help me understand this diagram better?

5377

[greenteagod]

I'd just do the wiring based on that website you linked. It seems to be a lot easier diagram to follow. Just add a T to where the original sensor was so you can put the old dummy light sensor and the new switch in place right there and wire like this

5380

[camoit]

Sooo whats the reason behind having this hooked to your oil pressure? If the float bole and line is empty you will need to crank the crap out of it to get fuel in the carb before it starts. It's safer to have a system that shuts off if you loose fuel pressure because the line broke or came off.

[greenteagod]

So from my understanding, this is a safety issue. If for some reason the engine stops then it kills the fuel pump as well. In the event of a wreck you might not have your senses about you to stop pumping gas on an engine fire or something else bad going on. It seems there would be more situations where you'd lose oil pressure and want the fuel to stop rather than losing fuel pressure and wanting the fuel to stop.

Not that I've done this mod just yet, I am waiting on a couple parts, but I actually did have a friend who had an old 240z and that thing burnt to a cinder because he had a rear mount battery and electric fuel pump. Engine caught on fire and it basically just emptied the entire gas tank in to the fire because that was still operational.

I'm not trying to speak on behalf of pennyman or anyone else so I'll definitely let them chime in about that.

That is true about the lines emptying, but pennyman says he's been running this setup for a good long while. I wager he can attest to that aspect of it.

[camoit]

You could always add in the two systems so it can shut off aether way.

[BradMph]

There is also the impact sensor that can be used to shut off fuel. Though you need a reliable one and probably more then one. Front/Back or a central located sensor. The ole 2 wire airbag sensor could be modified to control fuel since it detects an impact. I am really thinking more and more on this type of shutoff because some people have had issues with oil switches if they get a switch that shuts off fuel at a higher oil pressure rating then the required switch settings. They roll up to a light with a quart low of oil and engine shuts off. Our trucks, well atleast mine is getting older and oil pressure is not on viagra anymore, so it does drop lower then normal. I am though going to try the oil switch first, but if it causes a problem I am definitely going towards an impact/roll over sensor.

[pennyman1]

The oil pressure switch only needs 5 psi to switch, so if you are dropping below that at a stop, you got problems. Also make sure the oil pressire switch has a large hole in it so it doesn't clog from an errant piece of sludge. Use a switch like this: http://www.ebay.com/itm/310333238965?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_12655wt_1327

[greenteagod]

I'd just do the wiring based on that website you linked. It seems to be a lot easier diagram to follow. Just add a T to where the original sensor was so you can put the old dummy light sensor and the new switch in place right there and wire like this

5380

Just hooked my own up followed this diagram. Worked fine on the first try. Tried following the other diagrams and they weren't dumbed down enough for me. Either way, works!