BLKMGK Posted June 13, 2001 Share Posted June 13, 2001 Reading through the JTR directions they mention splicing into the wiring harness to rigger the fuel pump. The JDM Zs had electric fuel pumps and the wiring in the US market versions is there too but not used. When you break into the wiring harness up front where JTR mentions you'll find at least two green wires, one is much thicker and is what you want. I checked mine with an Ohmeter to be sure Anyway, a question and a tech tip. First - where does that green wire lead to on US Zs? Is it powered from the ignition circuit or what? Did the ysimply just leave the fuel pump off the US Zs and keep the wiring there? If so why are we splicing into the circuit at all - just to get the oil pressure switch in?! Is it ignition switched on JDM Zs? Just real curious since JTR tells us to CUT the silly harness - yuck! Secondly - for those of you using this wire do NOT splice into the harness - that's silly! Follow it up under the dash on the passenger side where there's a ton of connectors from the engine bay. You'll find that the thick green wire has a bullet connector up under there and you can disconnect it, crimp on your own "bullet" and run the wire into the engine bay with NO cutting of the stock harness I checked min with an Ohm meter and it's the SAME wire but I'd suggest you do the same to be sure. Anyway, thought I'd share and was hoping osmeone else might know where else that wire gets routed. With my cage I cannot easily follow it after the bullet and I was actually pretty lucky to find that connector at all - it was a surprise when I was trying to see where that wire migh lead. I don't see a thick green wire at the fusebox (sigh). Would the wiring diagrams show us even if it's not being used? If I'd had a battery in the car I'd have simply turned the ignition on and checked but... P.S. The black wire in the back for the old fuel pump ground is grunded on my car about 6 inchs back right to the frame. That wire doesn't go far at all and is the new ground for my Holly Blue Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 13, 2001 Share Posted June 13, 2001 Paranoid Pete here again. I used the stock wire to energize a relay at the fuel pump. Then I used a dedicated 12 gage hot wire (fused at the relocated battery) and ground wire (from the battery) to power the pump. I agree, find where that green wire comes out under the dash and tap into it at the end. BTW, my 73 only had one green wire to the pump area, and it wasn't very big. Also, I used the green wire at the dash to hook into a oil pressure safety switch to power the relay only when oil pressure (above 5 psi, for the Summit sourced switch I used, IIRC). Of course, you need to energize the relay to get the pump to start while starting the engine. You can use a momentary switch for this to manually run the pump at start up. For me, a bunch of big capacitors, a resistor and a small relay did the trick, creating a delay-off circuit. Energize the parallel capacitors (in series with the small relay) with the key on (and hidden fuel pump/ignition enable circuit is enabled), and after the capacitors charge, it de-enregizes the relay, so that now the fuel pump relay can only get current through the oil pressure safety switch. A small resistor in parallel with the capacitors discharges them after the key is turned off. The fuel pump relay gets current from this delay-off circuit for about 30 seconds, long enough for the engine to start and supply enoug hoil pressure to teh safety switch for that circuit to supply current to the fuel pump relay. (And some people wonder why this project is taking me so long!) Anyway, if you'r putting a fuel pump in the rear, be aware they can draw a good bit of current at full flow under pressure, and that long length of OE wire may not be sufficient. I added the relay back there since the battery was closer to the fuel pump than the dash, so I figured I'd have less voltage drop from the battery, to the relay near the pump then to the pump. Also, I suggest a oil pressure safety cutoff switch to energize the fuel pump relay. Quote Link to comment Share on other sites More sharing options...
Greg SmileZ Posted June 14, 2001 Share Posted June 14, 2001 Lone, My brother has a '32 Ford with a SBC (show type car) and that hex nut on the oil filter is where he mounted his oil pressure sending unit. It does make for a very clean look. Greg Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted June 14, 2001 Author Share Posted June 14, 2001 Pete - my green wire (only one back there) is used for a relay setup from Painless wiring. Since this car is carb'ed for now there's no big deal about it energizing right away as there SHOULD be fuel in the bowls. I guess maybe a jumper to a momentary switch might be a good idea for those times when th efuel boils out (sigh). I don't think I'll go quite as far as you did Still - where does that green wire go? What's it hooked to stock? Do we need to splice into it at all or can we use it to trigget a relay as-is? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 14, 2001 Share Posted June 14, 2001 Thanks Greg for confirming that. I may just have to put mine there, seems to make good sense.. Regards, Lone Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 14, 2001 Share Posted June 14, 2001 Stock, it depends on the year. Many of the 73s had it hooked up, and a relay, harness from the relay (on the right kick panel), in-line fuse, etc. were added to the US cars. The overseas cars had the electric fuel pump and wiring standard. Anyway, it was part of a fix for vapor lock in the 73s, I believe. So if your car doesn't have the relay, inline fuse, etc. it probably didn't go anywhere, just was hanging around in the harness. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 14, 2001 Share Posted June 14, 2001 On a somewhat related topic, I noticed when I was putting my engine in, right above the oil filter boss was what looked like a plug (hex head plug) does this lead into the oil passage and if so could one use it instead of the 't' arrangement that JTR suggest for the fuel pump cut-off? Might be less kludgy looking if thats the case... Thanks, Lone Quote Link to comment Share on other sites More sharing options...
Guest dankinzle Posted June 15, 2001 Share Posted June 15, 2001 Hey Pete, you didn't happen to major in electrical engineering or anything did you;-)? That wiring scheme for the fuel pump is a very cool and creative idea. Me, when I was wiring the MSD box in, I took the old wire going to the bat+ on the hei and wired it into a switch panel so the things stay on when you crank. Switch panel has fan, ignition, fuel pump, plus one other. Don't have to worry about the fan cause it has a temp switch. Everything from there is wired into relays. Oh as a side note, this may seem like duh, but I was banging my head over how to get the fan to do on/off/auto using a 3position switch. My problem was trying to always manipulate the switched power going INTO the relay. Didn't even think about messing with the ground from the relay. Wired ground from relay into the middle position. The two other positions go to the temp switch and directly to ground. And voila. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 15, 2001 Share Posted June 15, 2001 Yeah, MS in Mechanical Engineering. We did have a few EE classes though, and RC circuits are pretty simple. Actually, I got the idea for a delay off-relay circuit from an auto electronics site (can't remember where). I like that solution for a on-off-tempsender switch - cool. Ask Mike Kelly how nutso my cooling fan relay circuit is - he saw the schematic. It has about 10 times the functionality needed, but I didn't know how I wanted it to work so I made it do a bunch of stuff I can select in and out with a few switches. What I was going for was finding a set of operating parameters (temp sender and A/C trinary switch signals, manaul override switch) and three fan speeds (off, low, high) that would work best, without having the fan on if not needed. Playing with a bit of electronics is just another fun part of the car hobby to me - I do stuff on my car that's not necessary, but it's fun for me to design and build it. Quote Link to comment Share on other sites More sharing options...
jeromio Posted June 15, 2001 Share Posted June 15, 2001 On my 71 the green wire goes to the accessory relay which is energized by the ignition on switch position. I confirmed this by disconnecting the accessory relay and the fuel pump doesn't come on. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted June 15, 2001 Author Share Posted June 15, 2001 Hrm, I've got a metal can on the passenger side just under the dash - bolted on top of that darned cardboard thing. Is that the relay? It control anything else? I also noticed for the first time that a ton of the electrical stuff under the hood is there with disconnects. Never noticed that before - kinda' crowded! If I could just find the connectors I need I could have my wiring done. Will have to hit a different stereo shop when I get home today.. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 16, 2001 Share Posted June 16, 2001 Jim, there are a bunch of metal can relays on a bracket at the top of the right kick panel below the dash. Some were factory, other(s) were probably added at the dealer for dealer in stalled A/C. Not sure whether the fuel pump relay was there to begin with from the factory or not, but I think it was. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 16, 2001 Share Posted June 16, 2001 I know there is one there that definitely snaps on when you turn the key. If its the one I'm thinking it is (mounts right above the pass. side vent control cable mechanism, it seems I remember one of the wires (like the black/yellow) running through it.) Its a mystery to me what it does, I tried following the diagram in the chassis manual and even with my fancy no-line bifocal's I was unable to follow it. *shrug* Regards, Lone Quote Link to comment Share on other sites More sharing options...
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