proxlamus© Posted January 19, 2007 Share Posted January 19, 2007 Specs - Megasquirt n Spark 2.2pcb 021u code. 83 dizzy, GM HEI and stock igniton coil. Ok.. I was driving down the road.. and all of a sudden the car died. I pulled into a neighboorhood and began some tests.. I have fuel pressure.. the plugs are wet so it is spraying fuel. I pulled the spark plugs.. NO spark. I pulled the spark electrode wire out of the coil.. and since I had no multimeter I cranked it and held onto the electrode, I definatly got one hell of a shock. I assumed it was a cap/rotor. So i replaced the cap and rotor... and no spark! Hmm.. I tested the coil again and there was no spark and no shock Now to source it down... the coil is an original 1978 coil, So i replaced it with a MSD Blaster 2 coil. Car fired right up, drove it home, died in my driveway. No longer ran, and would no start. I am assuming it was the GM HEI setup, so I put in a NEW GM HEI module.. still no start. The problem is, I am not getting any spark out of the coil.. and is not sending any spark to the dizzy. My only other assumption is the DIZZY is bad.. and is not sending a signal to Megasquirt. So I measured the voltage on the GM HEI to see what was going on. (INCLUDED IS A DIAGRAM TO HELP) B (goes to + of the coil) = 12v C (goes to the - of the coil) = 12v W (GM HEI ground) = 0v (obviously its a ground) G (attaches to Megasquirt) >>> [ 1)On initial turn key to ACC, the fuel pump primes, and the voltage is 12v for a few seconds. I am assuming MS is sending an signal to the GM HEI which is why I can sense voltage. 2) In addition I can read 12v while cranking at this terminal. 3) The voltage reads ZERO (0 volts) when the key is on ACC and the ignition is live, untill I crank.] Now.. I have NOT read the voltage from the dizzy to megasquirt since I am getting postive voltage from MS to the GM unit (if the dizzy is bad will this still show a reading?!) The coil reads 12v and is getting power. Could this be a problem with 1) Megasquirt? 2) DIZZY 3)coil wiring ?? Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted January 19, 2007 Share Posted January 19, 2007 The way that is set up, you will see 12 volts on the G pin when Megasquirt is not sending a signal, and Megasquirt needs to actively turn on a transistor to bring the voltage down to zero. The first thing to look at is whether you're getting any RPM while cranking. If you do not see any RPM, the problem is on the input side - there is no signal from the distributor, or it isn't reaching the Megasquirt CPU. If you do get an RPM reading, but no spark, the issue is with the output side. To see if the problem is inside or outside Megasquirt, try plugging it into a Stimulator. On the Stim, you should get an RPM reading if the input is working, and have the FIDLE LED blink if the output is working. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 19, 2007 Author Share Posted January 19, 2007 I have a reading of 100 RPM while cranking the engine. So the issue is with the output side of the GM HEI? or with Megasquirt? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 19, 2007 Author Share Posted January 19, 2007 Oh in addition... included in this picture.. where the BLUE wire coming from the NEGATIVE terminal of the coil.... does megasquirt still use this "resistor?" Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 20, 2007 Author Share Posted January 20, 2007 OK.. I bypassed that "coil resistor to be safe... no luck... I am checking the voltage on the coil terminals.. I am getting 12v at the POS and 12v at the NEG! whoa..I should not be receiving a 12v source at the negative terminal should I? Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 20, 2007 Author Share Posted January 20, 2007 Ok.. I guess the neg and pos reads 12v untill the GM HEI tells the coil to fire... then the negative collapses and turns to ZERO.. another thing.. I used a volt meter and hooked it up to the TACH on the relay board (dizzy input) I have a reading of ZERO volts... on the TACH input.. does this mean I am not getting a dizzy signal?! Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted January 20, 2007 Share Posted January 20, 2007 If MS is getting an RPM signal when you crank then I bet your dizzy is probably working fine. Has it snowed/rained recently by any chance? My 280z is going crazy from the rain, like refusing to start or backfiring then dying while driving. Turned out it was water at the fusible links and stuff. But today it just plain refused to start and I had to buy starting fluid... never ever had this problem before. With MS at least you can do something about it. Plug in your laptop and make sure all the sensors are in the appropriate range. If you're getting fuel, you might have fouled out the spark plugs. (NGKs seem to be really sensative to fouling). You can also do a gate test on the HEI module. If your HEI and input checks out you might have somehow damaged the board's output side. Mario Quote Link to comment Share on other sites More sharing options...
mario_82_ZXT Posted January 20, 2007 Share Posted January 20, 2007 Here's the gate test. http://www.zcar.com/forums/read.php?f=1&i=556620&t=556549#reply_556620 That's Tony D schooling me on my wiring on my install about 2 years ago haha. Mario Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 21, 2007 Author Share Posted January 21, 2007 Ok .. I tested the HEI... wtf its brand new... I did the following + has "B" and 12v connected - has "C", "W" is ground, "G" is FIDLE I left out the condenser.. this is ok right? I then used a wire and connected it to the "G" terminal of the HEI unit. I then pressed it against the + side of the coil... Nothing.. No spark.. nada So why all of a sudden did this NEW HEI go bad? Now what? Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted January 21, 2007 Share Posted January 21, 2007 I'm telling you man...ditch the HEI crap and go with the MSD. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted January 21, 2007 Author Share Posted January 21, 2007 Well... its 21* F outside right now.. car is buried in 5 inches of snow and a wind chill of 2* F... I went to Advance Auto and had them test my HEI units... One was bad.. the other was on/off.. I grabbed a new one.. and hooked it up. After some reading I found out the base of the GM HEI needs to be grounded to a heat sync or metal... I sanded down the heat sync... added some di-electric grease... and hooked it all up. Problem solved.. bad GM HEI unit.. I shorted the other out... Cause? improper grounding of the base of the HEI unit.. YES all connections were correct, but it was all due to a corroded heat sync and improper grounding of the base of the HEI. Quote Link to comment Share on other sites More sharing options...
LineC Posted January 21, 2007 Share Posted January 21, 2007 I know you already solved your problem but the plugs won't fire just dangling out of the engine they need to be grounded to something like the strut tower or yourself . Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 21, 2007 Share Posted January 21, 2007 Ok ..So why all of a sudden did this NEW HEI go bad? Grounding, or Heat Sink Misapplication. If they are not properly grounded, and potted with heat conductive paste to a heat sink surface, they will fry really quickly. And as I posted in the other thread elsewhere, I went through some "New" aftermarket units from Wells / Autozone that were not much better than DOA. The only time mine started working was with the premium aftermarket unit from Perlux (Flamethrower) and that one worked wonderfully. The best I ever got out of the stocker aftermarket wells HEI module was a bluish/purple/reddish spark that jumped maybe 1/2" at the most... Quote Link to comment Share on other sites More sharing options...
mobythevan Posted January 22, 2007 Share Posted January 22, 2007 All of the HEI units I have seen are intended to get grounded through the bolt hole(only one of the two bolt holes has a metal ring rising out of the plastic housing), so if you don't bolt it to something on the car that is grounded you are going to be in trouble. Quote Link to comment Share on other sites More sharing options...
evildky Posted January 22, 2007 Share Posted January 22, 2007 quick easy way to test the dist, pull the fuel pump fusem, pull the dist, hold it's base to a ground and rotate the shaft, you should hear the injector relay and the injectors clicking, it not you got a dead dist Quote Link to comment Share on other sites More sharing options...
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