ComicArtist Posted August 29, 2011 Share Posted August 29, 2011 Still cranking, still won't fire. I've replaced the engine relays, dropping resistors, even a few of the injectors in an effort to get the thing to fire, but it won't. I have the fuel rail pulled out at the moment, with the injectors still hooked up so that I'll be able to see if they start firing. Used a multimeter to test it, and the wiring harness has a complete signal all the way from the injector plugs to where the ecu plugs into the harness. So I figured it was the ecu. Tested it with two other ECU's today, one of which I knew was good, and it still didn't work. Any ideas? It's a '78 ECU and harness. Quote Link to comment Share on other sites More sharing options...
rossman Posted August 29, 2011 Share Posted August 29, 2011 So you are saying that you are not getting +12v at the injectors and the harness path from the ECU to injector connector is good? Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted August 29, 2011 Author Share Posted August 29, 2011 Yes sir. That's exactly my problem. I'm about to check the signal from the distributor to the ignition module, providing the ECU with signal to fire the injectors. Hopefully that'll make a difference. Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted August 29, 2011 Author Share Posted August 29, 2011 I can't even find the path from the distributor to the ECU. You guys have no idea how much I hate and suck at wiring problems. I don't think I've ever seen so many wires in a harness before. Like, I'm on the verge of scrapping this project and selling it as a shell. I've had the motor in this thing for the last six months and the injectors refuse to fire. Basically, this is what I've done since it's ran. It blew a headgasket, so I bought an '81 L28et longblock from a guy locally. Pulled the original motor and engine harness, painted the engine bay, dropped the new longblock in. I did swap my working original distributor in it. Plugged the original working wiring harness back up to the original working ECU, and nothing happens. The injectors just won't fire. The harness path from the ECU to the injectors is good, so I'm assuming the signal from the distributor to the ignition module to the ECU is not going through. I'm going to the salvage yard on Wednesday to pick up another distributor and ignition module to see if that does anything. If not, I'm probably going to swap in an entire new engine/interior harness, hoping that fixes something. I really hate to do that, but I don't really have a whole lot of choice. If that doesn't work, I'll probably just resort to selling the whole thing. I've put way too much money in this thing, and it's about drained my resources. I love this car, and I have for a long time, but it's not leaving me a whole lot of a choice. Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 29, 2011 Share Posted August 29, 2011 You should have 12+ volts at the injectors full-time when the key is On. The ECU works by providing a ground for the circuit to energize the injector solenoids. It doesn't provide power, it provides a ground. If you don't have 12+ at the injectors, you might have a blown EFI fusible link (or you missed something when you put the new harness in). They are the two green links from the battery positive post. I think that they are pinned to the side of the relay box by the battery. Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted August 30, 2011 Author Share Posted August 30, 2011 I actually converted the four fusible links to blade style Maxi fuses. However, I noticed that the two green wires by the harness aren't hooked up to anything, but there's nothing for them to hook up to. I'll put up a picture tonight or tomorrow when I take one. The car's actually in my friend's backyard, since I live at an apartment. Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted August 30, 2011 Author Share Posted August 30, 2011 So whenever I put the harness back in there was nothing for this to plug into . It's the harness that runs across the top of the firewall to the fuse box and has like one relay on it and then those two green fusiblelink looking wires. Are these supposed to be plugged into somethings? Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 31, 2011 Share Posted August 31, 2011 (edited) Lucky coincidence - I have a 78 EFI harness in the garage and I was just looking at it (trying to figure out the Pin 1 path to coil (-), but that's a digression). Here is a picture of the piece that you're missing. It supplies power to the EFI relay which powers the injectors and a few other things. The ring terminal on the end of the white wire bolts directly to the battery positive. If you rig up your own connector you should make sure you use heavy gauge wire. Those are two ~40 amp (what seems to be the consensus for green) fusible links in line. Edit - I believe that that is a typical Nissan factory splice combining those two wires from the battery to the connector. Edited August 31, 2011 by NewZed Quote Link to comment Share on other sites More sharing options...
ComicArtist Posted August 31, 2011 Author Share Posted August 31, 2011 Lucky coincidence - I have a 78 EFI harness in the garage and I was just looking at it (trying to figure out the Pin 1 path to coil (-), but that's a digression). Here is a picture of the piece that you're missing. It supplies power to the EFI relay which powers the injectors and a few other things. The ring terminal on the end of the white wire bolts directly to the battery positive. If you rig up your own connector you should make sure you use heavy gauge wire. Those are two ~40 amp (what seems to be the consensus for green) fusible links in line. Edit - I believe that that is a typical Nissan factory splice combining those two wires from the battery to the connector. Holy fawk I believe you're my hero and you just saved my life. No exaggeration there either. I'm truly grateful beyond measure. I'll pick one of those up at the salvage yard tomorrow if the 77 they have out there has one. The wiring harness is somewhat strewn about but hopefully it'll be there. Quote Link to comment Share on other sites More sharing options...
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