mobythevan Posted April 10, 2003 Share Posted April 10, 2003 I found something interesting in the way that a 240 ignition siwtch works vs the 280zxt ignition switch. This is based on the schematics in the Haynes manual for both cars and could affect the turbo swap. First the 240 switch provides voltage to the coil when in start position(through G/W wire and through tachometer). During this time no voltage is sent out the B/W wire. However, when in the run position the switch then sends voltage out the B/W wire (through ballast resistor and through tachometer). This is fine gives you voltage on the coil during start and run. But on the zxt the start signal only goes to the ECU, via plug #2 yellow wire on EFI harness. The B/W wire from a zxt ignition switch provides the coil voltage during start and ignition. It boils down to the fact that the zxt ECU was only intended to see the start signal during starting. I don't think you can easily wire this in using the 240 ignition switch because they operate different. The 240 switch provides coil power through two different wires during ignition and start(these are then wire OR'd so you can't connect in anywhere for a start signal). The 280zxt switch provides coild power through one wire for ignition and start and then provides a separate wire to signal start. Now the question, does anyone know exactly what the ECU does different (if anything) when it sees the start signal. I suspect most people who have done the swap just wire the start signal in with the ignition signal and this notifies the ECU that you are "starting" all the time. This is easy enough to test by putting a separate switch on this start line and see if does anything I can tell when the engine is running, but I figure why re-invent the wheel if someone already knows the answer. I'm sure someone has noticed this, but in the 50 plus posts I've read so far no one ever mentions it. I figure this must mean that there are no side affects of having the start signal all the time. But I also see a bunch of posts saying that turbo swaps into 240 cars never seem to run right. Sometimes there are a lot more opinions than answers. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 10, 2003 Author Share Posted April 10, 2003 And the answer is http://www.zcar.com/forums/read.php?f=1&i=215827&t=215827 Had to do a lot of searching to dig up that post, but answers my question to the start signal. I am going to check the ignition switch tonight and make sure it operates like the schematic says. If so I will probably add a diode to effectively split the start signal to the ECU but also provide coil voltage during start. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 10, 2003 Share Posted April 10, 2003 It is supposed to see voltage at start, dont think I got to the point of finding out what you discovered though. I believe that is pin9 on the ECU IIRC on my 82, if you look at the black connectors on the ECU they are numbered, the middle connector has 1-10 on the top, and 11-20 on the bottom I guess. Have you found anything odd or wierd with the IGN relays? I am still not sure why my car wont start, I can only imagine its the injectors or maybe the distributor since I haven't checked signal yet. I've traced every single wire I have now going back to the ign. With what wiring I do have, I am just not sure about those IGN relays, I have to pin those out I guess to see if that jogs anything in my brain as to why the car isn't starting. The ECU gets power, the coil gets power, my fuel pump is hard wired seperately and gets power. I'll take a look at mine for kicks I guess and see whats up with signal/run, my brain just isn't remembering. Pin 9 and 5 are the ones that were "important" that I can recall. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 10, 2003 Share Posted April 10, 2003 Did you see voltage in the ON position? I dont recall that I did... I do know though from memory, that start is 3 wires on the 240 and 4 on the 280... Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 10, 2003 Author Share Posted April 10, 2003 I should have explained better, but the moral of the story is: you don't want to hook the start signal of the ECU so that it sees voltage all the time. That is what I gathered from the schematic, but the the signal I was going to hook it to on the 240z would not have worked. The ECU should only see this start signal when you are cranking and thats it. This won't keep the engine from running, but will keep the computer from going into closed loop mode, which causes the engine to run rich at idle and cruising speeds. Did you get your B/W wire from the igition switch connected up? Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 10, 2003 Share Posted April 10, 2003 Yeah, a guy named Wayne explained that it needs to see voltage on START only, this is what "boots up" the computer he says, and bootup switches are nowdays often like a FET, not a physical always on or off like a relay. I visited those posts so I saw the open loop thing, most of the 240 writeups and people that have talked about it seem to say the swap is easy and there are only a couple things to check, ground this, pin this so it gets voltage etc, but there sure seem to be some supprises. If and when the car is running I'm definately going to write all this stuff up. I am already forgetting everything I went through yesterday, I have my notes at home... I can almost recall Y and Y/W being shorted to each other, so this could be another problem for me. The only thing BW is going to right now is to the coil ignitor... at least as best I recall, I should have put that in my other post that I have that wired up. I dont know if its supposed to go anywhere else. I have a great PDF from the FSM, but the ign stuff that it shows always shows it going off the fargin page. So I only have about 3 known IGN routing wires in pictorial form, everything else is tips "make sure yellow to pin 5" or etc. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 10, 2003 Share Posted April 10, 2003 Moby, which 3 plugs is Ian mentioning in this post? http://www.zcar.com/forums/read.php?f=1&i=253139&t=253135 These are computer plugs I believe, I do not think I checked BR/G on Plug 1 although maybe I have, if he had the pins listed it would come to mind better. I am guessing these are the computer plugs, except for the fuel relay. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 10, 2003 Author Share Posted April 10, 2003 Those plugs are not the plugs that hook directly to the ECU. Plug 1 hooks to the fusible link box. Plug 2 was just inside the firewall, I "think" it hooked to the fuel pump module. Plug 3 was right next to the green EFI relay in the harness. BTW, all of those connectors are white plastic if that helps. The ECU connectors are black plastic. All colors and wires match what he says on my harness so I think I'm in business. I also doublechecked everything he says against the schematic to be sure how things actually work, all makes sense to me at this point. I plan to finish my wiring tonight. My engine only came with the EFI harness, I did not get the fuel pump module, the FI cooling fan timer, any of the car harness, or the fusible link box. Doesn't look like I need any of that stuff, but just to let you know what I have in case my answers don't make sense to you. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 10, 2003 Share Posted April 10, 2003 Ok, yeah I know that other connector, by the fuel controller module. Most of the wires on the connectors seem pretty exclusive, although sometimes it switches from one connector to its mate, like that particular one has green and then brown... IIRC that is. I'll check later, of course... and thanks for the help Quote Link to comment Share on other sites More sharing options...
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