motomanmike Posted September 13, 2012 Author Share Posted September 13, 2012 I wish I had another ECU to try but i'll check the wiring. Maybe I can scoop up an ecu fairly cheap if that is my problem. I just grit my teeth every dollar I spend on this old setup thinking man i'm halfway to a MS system by now. Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 13, 2012 Share Posted September 13, 2012 Both sides are supposed to have 12 volts. It's one of the weird things about transistor control. The injectors are controlled by transistors in the ECU. They should all have 12 volts on each side. I couldn't explain the magic behind it but I just went and checked one of mine to be sure. 12 volts on each pin with key on. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted September 13, 2012 Share Posted September 13, 2012 Update, I think I found the problem or part of the problem doing some testing really quick this morning. On 2 of my front injector plugs, I have 12v on both sides of the pigtail plug. Seems my problem may be deep in the bowels of this harness somewhere, they have to be rubbing or broken at a similar spot to pass through. I hope this hasn't ruined the ECU. The injectors (all of them) are supposed to have 12V - and due to their nature (the injector is a coil, a solenoid) they will show the same voltage on each side when power is applied. The ECU fires the coil (injector) by grounding one side for less than a split-second... The proper tests are that they all have voltage (my L28ET has constant voltage to the injectors - they are wired direct to the BAT through a fusable link as per the FSM circuit diagram), with the connector removed they should have approx 2.8 Ohms resistance across the two pins, and a noid light should respond (light ON when the injector should fire) when the engine is cranking. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 13, 2012 Author Share Posted September 13, 2012 (edited) Yeah I think you are correct, they all have an individual positive feed and all batch fire from one common ground. What i'd like to try is to feed the 2 injectors that the plugs don't have correct readings on from another known good firing injector plug. If that is not a good thing to do maybe someone has tried it? My thinking is that if they all share a common ground I don't see why I couldn't wire the 12v feed of the one side of the injector plug, then just cut the negative plug that makes the injectors fire at the ECU and run a dedicated new wire up to the injectors and save me the trouble of cutting this whole harness open. (this is all just a theory and may be totally in left field) Edited September 13, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 13, 2012 Author Share Posted September 13, 2012 CGSHEEN, are you saying both of the 2 pins on a single injector plug should have 12volts? 4 of mine have 12 volts on one side of the plug, the other 2 injector plugs have 12volts on both sides. Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 13, 2012 Share Posted September 13, 2012 CGSHEEN, are you saying both of the 2 pins on a single injector plug should have 12volts? 4 of mine have 12 volts on one side of the plug, the other 2 injector plugs have 12volts on both sides. Is that with the plugs connected or disconnected? Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 13, 2012 Share Posted September 13, 2012 Wierd thing is it will fire my cheap ebay noid light so i think the ecu will be ok. I would guess that your measurements are off. If your noid light fires, the ECU is doing what it's supposed to do. Put an injector on each plug and see if you can feel or hear it clicking, or use a screwdriver from injector to ear, to make sure there's enough current to actuate each injector. The engine runs. You should be able to inspect spark plugs, pull injector connections to see if a cylinder is dead, check timing, etc. You're digging in to the things that aren't really related to the problem you initially described, and getting ready to fix things that aren't broken. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 13, 2012 Author Share Posted September 13, 2012 (edited) I didn't have much time tonight but the phenomenon is no longer present, all injector plugs only have 1 pin with 12v on each plug. All will fire a noid light. I know for a fact 2 of them had 12v on both pins this morning and I tied them together. Those were the first 2 I checked when I got home. Very odd indeed. I'll be able to do more this weekend testing I'll get the motor started up and pull plugs all over and see if I find one that has no affect on operation when pulled. I'm not replacing things just to replace them, I'm not made of money so my frustration grew even greater last night. I will test the harness Saturday and see what I find I don't know if the reman AFM is even any good it doesn't fall in range with the FSM either and I read a post last night that said known good AFM test bad by FSM tests which to me is now believeable. Edited September 13, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 14, 2012 Share Posted September 14, 2012 For the record I measured on a 76 EFI system. Maybe the turbo system, with ECCS, is different. Watched your video. It kind of sounds like my car when I had the plug wires on in reverse rotation. It ran, but sounded terrible. Like yours. I notice you have an open exhaust. That can't be helping your O2 sensor signal. I don't know enough to guess at what effect a cold exposed O2 sensor would have on the signal to the ECU but it might be worth checking out. Good luck. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 14, 2012 Author Share Posted September 14, 2012 Interesting Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 14, 2012 Author Share Posted September 14, 2012 Nope dead on firing order I know it runs ok misting fuel into it and idled quite well before all vacuum leaks were plugged a few weeks ago testing. I'm baffled. I'll mess with it this weekend looks like this one will stretch into winter. I wanted it to be a summer project but that doesn't seem to be the case. It's kind of new to me carbed cars have never given me as much trouble as this 20 year old efi system lol. I have a Toyota truck and they don't break much so this all has been a learning experience and I haven't learned enough yet it seems. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 14, 2012 Author Share Posted September 14, 2012 (edited) Really suspecting the ECU the more I think about it. Why else would one single injector plug have both wires activated with 12v when I checked the other morning and then that night it be normal with very minimal moving of the harness? I wasn't imagining things, I checked those two plugs multiple times. I'm really baffled. That night testing those wires only had 12v on one pin of the injector plug and would fire a noid light. I don't want to buy more parts trying to fix a gremlin I can't find. The reason I keep leaning toward a MS system is i would know it is a "known good system and good harness" Yes its more complex but no matter what some may think by reading my posts I'm certain i'm capable of doing it. I don't have friends that have Datsun's I can borrow parts from and try. My other 240z is a carbed car. No one where I live even knows what they are half the time. I verified just visually the firing order last night. I need to pull the plugs and rotate the motor with a wrench and get it to TDC and see where the rotor in the distributor falls. It was right during assembly originally so I wouldn't think it changed at all. I really feel its in the injector cycle somewhere because of how it will run either misting fuel or starter fluid into the intake it runs fine. I know its firing a noid light but it seems dim to me looking at it. I really appreciate everyone's input. Edited September 14, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 15, 2012 Author Share Posted September 15, 2012 Would you think it has anything to do with the ECU now??? Looks like its growing some funk on the board. This car ran like this. Quote Link to comment Share on other sites More sharing options...
Gollum Posted September 15, 2012 Share Posted September 15, 2012 Bad diodes by the looks of the board labeling. If you can find the values I'm sure the board is fixable. The question is why they went bad. Could have been a wiring issue from the previous owner, or possibly something that happened to it during your diagnosis of another issue. I'd also check for obviously bad caps, they can wreak havoc on any circuit and electrolytic caps are bound to fail, and 25+ years later are quite ready to blow. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 15, 2012 Author Share Posted September 15, 2012 (edited) It looks like corrosion to me but I guess its the inside of the diode melted out. It only appears to be on the white diodes, the rest of the board looks normal. Its all over the board like this in spots, where the white and blue diodes are. I may have hooked up something wrong initially trying to get fire and spark or would imagine some pins were crossed because there was some serious rust flakes from the case of the ECU laying on the board itself when I opened it. They probably conducted power where it shouldn't go laying across some of the pins. I havn't made a decision on what i'm going to do yet but I think this would be a problem with why it wasn't running right. Really thinking i might let it sit until I can save enough for MS. If I can find a cheap ECU under $50 or something I might try it but anything more than that i'll probably just save my money up and go for the gusto. Edited September 15, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
Gollum Posted September 16, 2012 Share Posted September 16, 2012 At this point I'd be looking for a Z31 turbo being parted out. All you need is the ECU, MAF, wiring clips for both, along with the Dizzy chopper wheel. http://forums.hybridz.org/index.php?showtopic=26230 I've considered it but at the local picknpull they'd end up wanting over $200 for everything, at which point I could almost build my own MS2 ECU, which i just crazy. The other downsides is that the Z31 ECU doesn't like to run ignition at the RPM's the L motor CAN run, but if you're using the stock valvetrain don't worry about that. The other downside is that programming them ends up be more complicated and not much, if at all, cheaper than MS. But if you're only looking to push 300hp it's phenomenally better than the stock L28ET ECU. Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 16, 2012 Author Share Posted September 16, 2012 (edited) Lets just say a credit card is a good thing sometimes. MSII pcb3.57, stim, harness and cables/sensors on the way soon, ordered today. I have to source a tps sensor and get a wideband. I couldn't bring myself to spend any more money on something I couldn't truely control. It will be tough to get it going from here but i'm sure but i'll get it. I 'll let you know how it goes guys. This could be a very long road ahead so it may be awhile LOL. I pulled all the old harness out and bolted up my MSA downpipe and blocked off the EGR today. Still moving forward. Edited September 16, 2012 by motomanmike Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted September 16, 2012 Share Posted September 16, 2012 At this point I'd be looking for a Z31 turbo being parted out. All you need is the ECU, MAF, wiring clips for both, along with the Dizzy chopper wheel. http://forums.hybridz.org/index.php?showtopic=26230 I've considered it but at the local picknpull they'd end up wanting over $200 for everything, at which point I could almost build my own MS2 ECU, which i just crazy. The other downsides is that the Z31 ECU doesn't like to run ignition at the RPM's the L motor CAN run, but if you're using the stock valvetrain don't worry about that. The other downside is that programming them ends up be more complicated and not much, if at all, cheaper than MS. But if you're only looking to push 300hp it's phenomenally better than the stock L28ET ECU. LOL why does everyone forget about the O2 sensor! The L28et system has a single wire o2 sensor that uses the exhaust as the ground. The Z31 models had a HO2S with 3 wires and second ground through the exhaust pipe... Steel the HO2S wire harness from the donor Z31. Also early and late Z31's have Zirconia or Titania sensors which correspond to the ECU. Make sure it all matches when your pickin and note the production date on the donor just in case(I write it on the ECU). Ive contemplated using the RB25 harness, injectors, and a few other sensors on the L series. One particular setup I have would be a great platform for this. Id run the Apexi PowerFC though for full programming with the FC-HAKO or FC-Datalogit. Its a lot of money, but in the end its still cheaper than full stand alone components and I already have most of the components in bulk laying around. But the engine I have should be good for the better part of 500hp. My biggest problem is that I already have MS and EDIS and no cars currently that would be worth putting it all into. BTW its KTM's old L28 bottom end. Anyway, now returning to your regularly scheduled postings. Quote Link to comment Share on other sites More sharing options...
Gollum Posted September 17, 2012 Share Posted September 17, 2012 Because who cares about O2 sensors? (oh yea, smog techs ) My L28ET sometime got BETTER gas mileage with the O2 disconnected. And even if it was the same or even slightly worse MPG then it was worth the trade off of driving better. Then again, just about everything with my ECCS is FUBAR... Quote Link to comment Share on other sites More sharing options...
motomanmike Posted September 17, 2012 Author Share Posted September 17, 2012 I got a wideband LC1 with gauge at a swap meet from a buddy for $65 this past weekend. He had an old supra project he gave up on. All new in box what a deal! I can't wait for this set up to get here. I've prepped by removing all the old harness and pulled off anything I won't be using with megasquirt. I guess this thread is dead now. I'll be posting everything else I have issues with in the future I guess in the EMS thread. Thanks for everyones help trying to troubleshoot this stock system. I concluded the ECU was indeed bad on it by the looks of the board and decided to go with a megasquirt system from DIY autotune. Mike Quote Link to comment Share on other sites More sharing options...
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