Z_Dust Posted March 13, 2007 Share Posted March 13, 2007 I have a 77z w/83zxt swap using MS II, PCB 3, direct coil (ZXT coil) control and relay board. I got the car to start, got the timing right and tuned the VE table a little bit, it was way too rich. The car was idling good and it would rev up to 3K RPM pretty good. I was happy!!! I went to start it again today and, well it didnt. I noticed the LED closest to the DB9 connector on the MS II will not light during cranking and theres no spark from the coil. Mega Tune RPM gauge shows zero while cranking and datalog RPM also show zero. It does have power while cranking but it doesnt seem to be getting a tach signal. I dont have a stim. I purchased it assembled. I double check all connections. Everything is the same way it was a day or two ago when it was runing fine. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 13, 2007 Share Posted March 13, 2007 Try connecting the laptop and loading your .msq file back into it then retry it. Also make sure you have spark output "going high (inverted)" in the ignition options. Also what is your max dwell set to. I think if it is higher than 4 or so you could burn the coil. http://www.megamanual.com/ms2/vb921.htm Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 13, 2007 Author Share Posted March 13, 2007 Its at "going high invertred" and dwell is at 3.2. I tried a known good coil with same results. I will try and reload the file and see what happens. Thanks Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted March 13, 2007 Share Posted March 13, 2007 It will need an RPM signal to get a spark. You can try turning the distributor slowly and seeing with a voltmeter if you get a 0-12 volt signal on the tach input line. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted March 13, 2007 Share Posted March 13, 2007 Z_Dust, are you using the transistor that sits right on the turbo coil or are you directly connected to the + - on thecoil? Just curious. Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 13, 2007 Author Share Posted March 13, 2007 Thanks for your replies As I understand the factory transistor is not used. The coil's "+" is connected directly to the #5 "slot" on the relay board with a 10A fuse along with the fuel pump. I'm going to work on it some more right now after I reload Megatune. I have read of some of the guys going MSD in order to get a stronger tach input. I wish I had a stim to find out if the problem is before or after the MS. I also noticed the main relay on the board gets quite warm compared to the other two. Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 13, 2007 Share Posted March 13, 2007 If you are not seeing any RPM in Megatune, then it is an input, not output problem. Something in the input trigger has gone wrong. Check all your input trigger connections. Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 13, 2007 Author Share Posted March 13, 2007 here's what I've done so far: Remove dizzy grounded the coil wire to ground and turn it by hand. I can hear and see the spartk going to ground from the coil. At the same time RPM gauge on Megatune responds to the rotation of the dizzy. So this tells me the connection and signal to MS is good, right? I did as Matt Cramer sugested and measuared the voltage coming from the dizzy's white wire as I was spining it. Every time it clicked it read 4.2volts (should it be 12v?). HOWEVER; I replaced the distributor, rewire everything, power up computer and MS, turn the key and to my surprise the tach on MS is not moving, no spark from the coil either. It seems to work fine until I turn the key, almost as if its loosing power during cranking. So I wired MS straight to battery just to eliminate that possibility but the condition remains. Any ideas? Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 13, 2007 Share Posted March 13, 2007 Do you have a 1k Ohm pullup resistor to +12v on the distributor output (pin 24 of MS)? Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 13, 2007 Author Share Posted March 13, 2007 Yes I do. I have it wired to the relay board on slot #15 1KOhm 1/4 watt resistor. I did replace it while troubleshooting just in case. What gets me is that it was working fine one day, then the next day it started doing all of this. Also I have been using the same battery for te last few days while trying to tune the idle and it may be getting low on charge. It is charging as we "speak". Could this be caused by a low batt? I hope not. That would be embarrasing Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 14, 2007 Share Posted March 14, 2007 Yes, a low battery can cause all sorts of problems. Mostly when you are cranking, as the voltage can drop dramatically if the battery is questionable. Even though the lm2937et-5.0 5V voltage regulator in the MS has a low dropout voltage of 0.5V, other devices in the MS can be effect by a low cranking voltage. As a last resort, I would try a different CAS sensor if you have one. It may be starting to fail, which would explain why it works with no load on it. Quote Link to comment Share on other sites More sharing options...
twoeightythreez Posted March 14, 2007 Share Posted March 14, 2007 Not to sound overly inquisitive, but you did verify that the distributor drive shaft is turning while cranking? (It's just the way you worded it...you turn the dizzy and get an input, put it all back together and no input???) I've never heard of one of these shearing the dizzy drive gear but it's still possible. (Though I'm betting it's not mechanical, but u never know) Quote Link to comment Share on other sites More sharing options...
twoeightythreez Posted March 14, 2007 Share Posted March 14, 2007 I also noticed that on occasion when booted into Megatune if the connection is lost the engine will stop running. (and won't start again until I reset the MS) Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 14, 2007 Author Share Posted March 14, 2007 Hey twoeightythreez, I want to first thank you because one of your old posts here at hybridz helped me in getting over some MS VE table issues. Yeah the dist shaft is still one piece and turning. I'll be trying again with a fresh and fully charged batt now that the baby (1mo old) is awake . The wife doesnt like it when I wake up the boy with teh Z (2.5in DP and exhaust straight back). Quote Link to comment Share on other sites More sharing options...
twoeightythreez Posted March 15, 2007 Share Posted March 15, 2007 Hey I just had an idea... This happened on mine too when I was getting the MSII running...I had the internal pullup in the MS but I had no spark...try a 1.2K ohm resistor right in the wiring from the distributor. e.g. just install a resistor between the B/W 12vdc wire and the G/B pin 24 wire. If you carefully trim back the coating on the wire on the dist. side of the connector you can easily install a resistor between the 12v on the dist and the input for MS. Plus, once you heatshrink it all back together it looks untouched. As you asked:"Every time it clicked it read 4.2volts (should it be 12v?)."--it should...possibly you're powering the dizzy from a 5vdc output by mistake? This might cause it to work fine under no load but once it's loaded (e.g. the voltage drops due to the power required to crank the engine) the voltage drops too low to generate a signal?? (this is why I powered the dizzy directly from the MSII input power lead...no voltage differential between the MS and the distributor that way...as the power and ground for both are coming from the same place....) I also replaced the connector, as mine fell apart one day while troubleshooting (the connector is 20+ yrs old after all)...A 4-pole trailer connector (use the ones for the lights, not the exposed ground) is watertight and works great. Also, make sure the distributor body is grounded to the engine block, in addition to the ground in the connector, (the distributor itself should have a spade sticking out from the body for this very purpose...if not just put a ring terminal on one of the bolts that fasten the dizzy to the timing cover) and make sure all the grounds under the hood with the exception of the negative battery terminal,(which should be grounded to the engine block as well) terminate at the same place as the megasquirt. (I just tied all the underhood grounds...which go directly from the block to the - terminal of the battery...together at the DB37 and grounded them to the Megasquirt unit....and I also added a few body grounds directly to the negative terminal as well) Also...since you're using a relay board (I chose to utilize the datsun relays that were already there, with a slight rewiring of the fuel pump relay, instead of a relay board) make sure the relay board is also grounded to the engine block and the megasquirt unit. Adding more grounds from the body to the negative terminal is also a good idea...it's simply not possible to have too much ground, especially when concerning an ECU, which computes things based on voltage differentials. (Think of the car's body in a neg. grounded DC system [since electron flow is actually from negative to positive terminal in a battery] as a huge junction block for all the systems installed in it and you get the idea...you want as small a voltage differential from supply to ground as possible) Also try isolating the power supply from noise which might just be confusing the heck out of the ECU. I hope this helps and that your Z starts terrorizing the neighbors, and maybe your best part of you (your kid) will start soundly sleeping to the sound of an L-series revving Good luck! P.S.-sorry if I nuked this thread a bit.... Quote Link to comment Share on other sites More sharing options...
Z_Dust Posted March 15, 2007 Author Share Posted March 15, 2007 I worked on all the grounds as suggested and charged the battery overnight. I now have a signal!!! The car starts, idles rough and as soon as I feather the throtle it stumbles and dies. Before all this I had it idling good and responding to throtle really smooth up to 3K RPM. Well at least now it wants to idle. Quote Link to comment Share on other sites More sharing options...
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