shawninvancouver Posted June 5, 2021 Report Share Posted June 5, 2021 I have a brand new msd coil. when car key is turned on i have power to a black/white and blue wire / I need to know which goes to the negative and which goes to the positive on the coil the wire diagram says black/white to pos and other to neg. i tried that and when i turn key to ignition nothing happens.. tried wires other way and nothing happened. i am very close as i have power going right to the coil but not coming out of coil.. i checked fusable links.. all look good.. what is wrong here?? the way the wires are hooked up? or is there something else im missing?? thanks.. can someone post photo of coil wiring Quote Link to comment
datzenmike Posted June 5, 2021 Report Share Posted June 5, 2021 Groan, I hate non stock parts. They almost never are as good, they act differently, have different primary and secondary resistances. Do you have a points ignition? My wiring diagram is rubbish for seeing the color codes. The negative terminal on any coil goes to the distributor where the points open and close a path to ground to cause current flow in the primary. The positive terminal of the coil has two supplies of power to it. One is the ignition switch in the ON position which goes through the ballast resistor to drop the voltage when the engine is running. The other is a full 12v when the ignition is in the START position. This by passes the ballast and supplies the coil with full battery voltage for hotter spark during start. If you have a test lamp or meter, find the wire that a/... comes on with the ignition in the ON position, and b/... the wire that has power in the START position. If you clip the test lamp the the battery positive, touch and find a wire the flashes on and off when the engine is being turned over.... this will be to the points in the distributor opening and closing a path to ground.. Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 ya.. i did those test. when the key is turned on just to power - both wires going to the coil have power pos and neg .. is that wrong??? only one should have power when key is on and other one when key is turned to start car?? if this is the case - what is going on?? does my car have an electronic unit under the dash?? i assume its a points car... if it has an old style distributor.. i assume its points... i cant post photos.. so maybe you can walk me through this.. its a 74 260z thanks Quote Link to comment
datzenmike Posted June 5, 2021 Report Share Posted June 5, 2021 If the points are open you will probably read some voltage through the coil from the positive side. You have a meter? connect to the negative side and turn the engine over with the starter. You should see the voltage go on and off as the points open and close. If it doesn't, take the distributor cap off and watch the points while turning the engine with the starter. They should open and close. The gap should be around 0.020" Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 Hi... my main question is a. should i see power to both pos and neg sides of the coil when i turn the key to the power position? b. does the black/white wire go to pos or neg? c. would a screw driver with bulb in it work to see power out of coil if it is going from end of coil to a ground on car? would it light up when car is turned to start position or not? does there need to be a gap? i was just poking it to a ground.... thanks Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 I dont have my diagram for a 260 in front of me but on all the previous S30s the black/white is your key on/crank 12v to the + of the coil. 260s and 280s have a transistor ignition module, they are mounted on the pass side kick panel, or kind of behind the right side of the glove box in that same corner. will look prob like this on the 260 other variations from the 280z... Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 ok.. but main question is... when key is in the on position ( not start ) should i have power going to both pos and neg of the coil?? does that mean things are working? what will the bad effect be if the ignition module is bad?? what color is wire to neg side of coil?? i think previous guys had all wires mixed up// Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 1 hour ago, shawninvancouver said: c. would a screw driver with bulb in it work to see power out of coil if it is going from end of coil to a ground on car? would it light up when car is turned to start position or not? does there need to be a gap? i was just poking it to a ground.... Are you talking about a test light? I suggest getting a multimeter and learning how to use it to check voltage and continuity at the very least. Knowing that will save you a lot of headaches in the future... Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 yes - using a test light --- Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 1 minute ago, shawninvancouver said: ok.. but main question is... when key is in the on position ( not start ) should i have power going to both pos and neg of the coil?? does that mean things are working? what will the bad effect be if the ignition module is bad?? what color is wire to neg side of coil?? i think previous guys had all wires mixed up// If your module is bad, you wont have spark. If you arnt looking at a wiring diagram already you are going to need to find one. You will need it and at least have a basic understanding of it. Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 Did you have spark before you put the new coil on? Quote Link to comment
datzenmike Posted June 5, 2021 Report Share Posted June 5, 2021 2 minutes ago, shawninvancouver said: ok.. but main question is... when key is in the on position ( not start ) should i have power going to both pos and neg of the coil?? does that mean things are working? what will the bad effect be if the ignition module is bad?? what color is wire to neg side of coil?? i think previous guys had all wires mixed up// No, power only goes to the _+ side of the coil and the - side is grounded by the points or the electronic distributor. Take the wire off the - side of the coil asn check it for voltage. You will read some coming through the coil from the + side. Just now, Skib said: Did you have spark before you put the new coil on? Good point. I hate MDS crap. Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 i could not find a diagram - even in the fsm that shows what color wires going to coil... do you have any idea on that?? \fudge... so if the module is bad i wont get a spark?? oh man... how can i narrow the problem down to the ignition module?? Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 maybe the points are closed... would that could power to neg side of coil? should i open points??? Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 other question is how to check for spank coming out of coil? can i test for that with bulb in screwdriver? when i try to start car would it light up if connected to end of coil and grounded? would it light up or not? does there need to be a gap? Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 If you have 12v both sides of the coil that means there is no load on the coil and the negative side is open circuit. Thats normal for electronic ignition when the engine isnt running. The stock 260Z dizzy should be electronic, thats what the module under the dash is for. Its basically a big ass matchbox, before the matchbox dizzy mike. Take your cap off and verify you are working with an electronic distributor or points. Not going to get far if you dont know what your working with. Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 1 minute ago, shawninvancouver said: other question is how to check for spank coming out of coil? can i test for that with bulb in screwdriver? when i try to start car would it light up if connected to end of coil and grounded? would it light up or not? No it will not. you can get these for like $5 at the parts store to check inline and it lights up like a test light. but you can stick a screw driver in the end of the coil wire and rest it on your shock tower so the metal has a bit of a gap to one of the bolts. and when you crank it over you will get a spark jumping that gap. if you have never done this go look up a youtube video or something. if you do it wrong you either wont see spark when there is some, or you might get a nice fat shock from the coil. Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 open this image in a new window full size. Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 ok.. so you are saying there should only be power going to the pos on the coil with the key in on position.. so why am i getting power to pos and neg? did they hook the wrong wire to the neg? is something else causing it? if points are closed would it cause power to neg? if the ignition module was bad would i still get power up to coil? that diagram does not show color of wire to coil.. or do you see something else? Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 Yes it does. White/Black is (+) and Blue is (-) Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 it does not show the + and - on the coil - what does that mean ? either side is ok??? Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 2 minutes ago, shawninvancouver said: if points are closed would it cause power to neg? if the ignition module was bad would i still get power up to coil? verify you actually have points. yes, the coil power comes from the ignition switch. Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 ohhhhh is the coil that thing at the bottom that looks like a sideways oil can??? 🙂 Quote Link to comment
Skib Posted June 5, 2021 Report Share Posted June 5, 2021 Just now, shawninvancouver said: it does not show the + and - on the coil - what does that mean ? either side is ok??? positive and negative are clearly labeled on that diagram..... Quote Link to comment
shawninvancouver Posted June 5, 2021 Author Report Share Posted June 5, 2021 whats the difference between BW and WB in the colors of wires??? black white white black?? or am i an idot? Quote Link to comment
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