HICKL Posted March 3, 2016 Share Posted March 3, 2016 Here we go, I am a former pretty active member of HybridZ on the V8 conversion side. Had a succesful V8 conversion that is now a daily driver but will run 11.50 on the 1/4 mile whenever I want it to. Have not done much with it over the last few years so have not been active here. I have recently adopted an 81 ZX turbo car with an MS3 ecm. The car belonged to a good friend of mine and it just died on him going down the road. Thru lack of time to mess with it, he passed it on to me. I am as ignorant as can be on the fuel injection/turbo/MS3 topic, so I have been doing a lot of research to get myself up to speed as much as possible before getting on here and asking too many newbi questions. Here's the story, car was running fine and died going down the road. No spark. I have re-traced all the wiring etc and all seems to be in order. My first thought was that the distributer was probably not sending a signal (its an 82-83 dizzy with the 50 mm optical trigger). Did some data logging and I see the ECM is recording RPM's so I guess the dizzy is doing its job. I then put a timing light on the coil wire to see if the coil is firing. It is not. I hoped was just a bad coil so I stuck that coil in my V8 car and it fired right up so the coil is good. (also tried another good coil in this car and no go). I am an old school guy so bare with me here. Is there a way to test the circuit at the coil to see if the MS3 is opening and closing the ground circuit as it should? I was thinking I should be able to take the ground wire from the coil an check continuity between it and a known ground and see if the circuit it opening and closing. Will this work? If not, any advise on troubleshooting this thing would be very appreciated. I know he did the BIP373 conversion and even replaced that pc after the car broke down to see if it was the culprit. He also had two MS3 boxes and both were working fine and the car won't fire with either one... I have the data log from when the car died as well as a short data log of me just cranking on it the other night. I am too green to know if there are any clues in there but can provide if of any use to anyone higher tech than me. Thanks Jeff Quote Link to comment Share on other sites More sharing options...
Metro Posted March 3, 2016 Share Posted March 3, 2016 Sounds like you're on the right track. If I read correctly, you've tested two other MS3 boxes with the car and it doesn't work with any? I would check the wiring for the coil to make sure it has power when cranking. Next see if it is receiving a signal from the ECU. You should be able to test the output from the BIP373 with LED and wire or a test light. It will be outputting a ground signal to the coil, so attach one side to 12v and the other to the coil (-) wire. It should blink steadily when you crank. Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 3, 2016 Author Share Posted March 3, 2016 I have tested with 2 boxes. The one that was in it when it died as well as a second one he had used in the car that had the same tune etc. I checked voltage across the coil with the key on and it was either 7 volts or 9 "ish". Can't recall as has been a few weeks so don't quote me on that. I will test the ground wire as you recomended! Thanks! Quote Link to comment Share on other sites More sharing options...
Metro Posted March 3, 2016 Share Posted March 3, 2016 The voltage for your coil sounds low, it should be around 12 volts. Also I'm not sure how your car is wired, but I always wire my coil to the fuel pump relay that Megasquirt controls. That means, the coil is only on when the ECU senses the motor is spinning. Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 3, 2016 Author Share Posted March 3, 2016 Will have to check again. It seems like it was 12 volts if I checked to a solid ground but lower if I checked across the coil terminals with the key on. Will confirm tonight! Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted March 3, 2016 Share Posted March 3, 2016 Are you using the stock distributor setup? if so you may have a bad ignitor... Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 Hey metro, just checked with test light. As soon as I turn the key on, the light comes on and stays on steady while cranking. Duplicated the test with an analog test meter checking continuity from negative wire to ground. As soon as ignition is on, I have continuity to ground and does not fluctuate when engine is cranking. I guess bottom line is ms3 is getting signal from dizzy, but not sending to coil... Brad man, see my original post for dizzy setup, if you need more info let me know. From what I understand, stock igniter no longer exists. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 4, 2016 Share Posted March 4, 2016 I checked voltage across the coil with the key on and it was either 7 volts or 9 "ish". This looks like a short on the negative post circuit of the coil. Probably why Brad-Man suggested a bad ignitor. Could just be a pinched wire or bad connector. Should be about battery voltage on both sides of the coil until MS3 grounds the circuit through the BIP373. In other words, battery voltage with the key on but engine not turning, then a voltage drop when the engine is turning and spark happening. Quote Link to comment Share on other sites More sharing options...
Chickenman Posted March 4, 2016 Share Posted March 4, 2016 (edited) OP mentioned this car has an 82 to 83 Optical Trigger, so no ignitor on Dizzy to worry about. My first thought was that the distributer was probably not sending a signal (its an 82-83 dizzy with the 50 mm optical trigger). OP are you getting strong signal counts on both Trigger and Home when you spin the Dizzy by hand? BTW, it may have been a Typo, but the trigger wheel in these Dizzy's is 54mm in diameter. Not 50mm. A 50mm Trigger wheel will fit, but it won't work properly. With distributor out of car, upside down with spline facing you. 4 prong Electrical terminal at 12:00 O'clock. Connections on Optical Dizzy are as follows. Trigger +12V Home Ground Check the 12v feed at the Dizzy. It should be a solid 12 ( or battery volatge ) when ignition is turned on. Then make sure that when you crank the engine, you still receive battery voltage at this connection. Grounds are critical and can do funky things. Check them all carefully. Dizzy ground should go to a clean stud or bolt on cylinder head or block. ( No paint or rust at this ground point ). All sensor grounds from MS3 should go onto this same ground point on the engine. Main ground from MS3 should go to same ground location on engine. Next... run a LARGE gauge ( minimum 10 to 12 gauge ) grounding wire or ground strap, from the same ground location on the engine directly to Negative battery terminal. Attaching grounds directly to the Negative battery terminal is a big No No. Edit: You don't believe you run a Ballast resistor with the MS. Edited March 4, 2016 by Chickenman Quote Link to comment Share on other sites More sharing options...
Chickenman Posted March 4, 2016 Share Posted March 4, 2016 Just another thought. Simple thing, but it's tripped me up a couple of times. Check the coil HT lead with an Ohm Meter to make sure it's still OK. Or try a known good coil lead. They can go bad, especially cheap brands such as Taylor and a few others. You should be using a good Spiral Core spark plug lead set such as NGK, Magnacore, or MSD. Absolutely no solid core wires or carbon resistance wires. Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 I'll have to check on that trigger wheel...that the information I was given. Am curious Chickenman about your advice on the grounding. From other articles I read as well as wiring diagrahms, I understood it as they want the MS3 firmly grounded to the block but all the sensors to be grounded back thru the MS3 box, not to the block. That is how mine is wired and it seemed odd to me, but seemed to be consistent with the instructions. I do have some concerns on my +12V feeds. It looks like they are all pulling from the same relay (its over by the battery, I assume its the original ignition relay but have not confirmed that) anyway, the voltage seems to be a little low coming out of that relay (10.5-11.5, fluctuates a little). Based on the fact that the MS3 was reading rpm's, I took that as telling me the dizzy was working properly. Is that not a sound assumption? Thanks again guys for all your input. This is uncharted territory for me so stumbling thru it as well as I can! Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 Just confirmed, it is a 54mm wheel. Quote Link to comment Share on other sites More sharing options...
madkaw Posted March 4, 2016 Share Posted March 4, 2016 Might need to direct your attention to that relay as far incoming trigger wire and associated grounds with that relay . Maybe swap out a relay and try. Quote Link to comment Share on other sites More sharing options...
Metro Posted March 4, 2016 Share Posted March 4, 2016 Hey metro, just checked with test light. As soon as I turn the key on, the light comes on and stays on steady while cranking. Duplicated the test with an analog test meter checking continuity from negative wire to ground. As soon as ignition is on, I have continuity to ground and does not fluctuate when engine is cranking. I guess bottom line is ms3 is getting signal from dizzy, but not sending to coil... Brad man, see my original post for dizzy setup, if you need more info let me know. From what I understand, stock igniter no longer exists. I'll be honest it's been a while since I've had to troubleshoot the ignitors and I'm going off of memory. I believe the light should flicker, if it's steady on you might have a short or something. How is your BIP373 mounted, is it in the case? As for grounds, you want all your sensor grounds to go to the same place (on the ECU) and then run the main MS ground to the block. What you have sounds correct. Also yes, your ECU is working properly if it's seeing a steady 250-300rpm while cranking. Could you upload your MSQ? The forum won't allow the MSQ to be uploaded, so zip the file first. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 4, 2016 Share Posted March 4, 2016 Still curious about the coil circuit. Were it my problem, I'd measure voltage at the plus and minus with the key on, then disconnect the negative post and measure again. Should be no change. There's typically other stuff on the coil negative circuit, like the tachometer. Any short that keeps current flowing can reduce or eliminate spark. The primary circuit's magnetic field has to disappear for the secondary circuit to produce a spark. That's just me parroting a variety of stuff I've picked up over he years, not a physics or electronics expert. Still, confirming the make and the break of the primary circuit will tell you something. No break, no spark. See breaker point ignition systems. Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 Ya, I understand the circuit has to break for the coil to fire. I did remove the tach wire last night just in case that was giving a ground path. I did bypass that relay one time with a direct 12v jumper just to see if it did anything. It did not. Here is a file of just me briefly cranking it over..I also have the data log of when it died. Will upload that as well if helpful. Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 oops, trying to attach file again.. 2016-02-29_10.50.18.zip Quote Link to comment Share on other sites More sharing options...
HICKL Posted March 4, 2016 Author Share Posted March 4, 2016 Metro, I just realized I attached a data log file and thats not what you asked for. Lets try this again. 2016-03-04_15.41.38.zip Quote Link to comment Share on other sites More sharing options...
HICKL Posted May 23, 2016 Author Share Posted May 23, 2016 Follow up, finally got it to fire up yesterday. Not running good yet, but is running. I found that my bip373 had shorted out between the metal tab and the ms3 box. It had all the right plastic and insulators in place, but it had continuity between the tab and the bar it screws to. I could barely back off on the screw and the short went away. Now I just have to get it tuned, idles really rough and is rich as heck! But it starts! Quote Link to comment Share on other sites More sharing options...
Chickenman Posted May 23, 2016 Share Posted May 23, 2016 Good diagnosing. Finding something like that is really tricky. Quote Link to comment Share on other sites More sharing options...
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