Dan Baldwin Posted October 10, 2002 Share Posted October 10, 2002 Hidey ho. I got the MSD 8920 tach adapter last night, and I'm trying to get it to make my 240z 4-wire tach work. I am CLOSE. The tach now works ONLY when I'm starting the car. As soon as I let the key go, tachie no workie. Currently (hee hee) the adapter is grounded, white wire to 6AL tach output, and red wire to the black/white stripe wire that used to go to either coil+ or the other side of the (no longer used) ballast resistor. Connecting the adapter to both the black/white and the green/white wires doesn't change anything. Anybody got an idea what I can do? I know that the ballast resistor is bypassed while cranking, so that must have something to do with my problem. Help! Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted October 10, 2002 Author Share Posted October 10, 2002 Oh yeah, using an MSD 6AL box. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted October 10, 2002 Share Posted October 10, 2002 My MSD tach adapter went just between the 6A and the coil. But My car is 78 so it might be different. I also had to use two diodos things to get the tach working. Quote Link to comment Share on other sites More sharing options...
spotfitz Posted October 10, 2002 Share Posted October 10, 2002 Thats funny considering I have a '78 tach in my '74 and I didn't need the adaptor. Did you find you had to have the adaptor after trying it without one? Quote Link to comment Share on other sites More sharing options...
yo2001 Posted October 11, 2002 Share Posted October 11, 2002 Well, with EFI, you need a correct volt from negative coil wire so my car wouldn't crank without one. Quote Link to comment Share on other sites More sharing options...
dmanzo57 Posted October 11, 2002 Share Posted October 11, 2002 Dan, I think you want to connect the red wire from the tach adaptor to the other black/white wire, +12V when ignition is on. Don Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted October 11, 2002 Author Share Posted October 11, 2002 Nope, it doesn't work at ALL when I do that. When I wire it to the OTHER black/white wire (only sees voltage when key is in start), then the tach works, but only when the key is in start! Maybe some combination of resistors and capacitors between the MSD and the switched 12v black/white wire... BTW, the switched 12v black/white wire goes to the tach? Damn I'm confused. He'p! Quote Link to comment Share on other sites More sharing options...
dmanzo57 Posted October 11, 2002 Share Posted October 11, 2002 OK, try connecting the green/white wire to switched +12V. The green/white and one of the black/white wires are connected together through a loop in the tach. I had the same problem, tach only worked during cranking, when I put mine together but it's been almost two years since then. Don Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted October 11, 2002 Author Share Posted October 11, 2002 That no work neither. Damn, this is infuriating. So far the only thing that does anything is hooking the black/white wire (the one that is only hot when starting the car) to the red tach adapter wire. Then I only get a tach reading while the starter's engaged. Grrrr... Goin home now. Dan Quote Link to comment Share on other sites More sharing options...
dmanzo57 Posted October 14, 2002 Share Posted October 14, 2002 Dan, I checked the wiring on my '72 this weekend. Here's what I've got: Black/white wire(previously coil +) connected to red wire from tach adaptor. Green/white wire connected to swithed +12V. I hope this helps. Don Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted October 14, 2002 Author Share Posted October 14, 2002 Will try it this P.M. Didn't make much difference at time trials yesterday, as it was wet and SLIPPERY during the timed runs. Short shifted everywhere. Thanks, Dan Quote Link to comment Share on other sites More sharing options...
Hybrid240z Posted November 20, 2002 Share Posted November 20, 2002 I have a 72 240Z with a Mallory Unilite distributor. I have a 280Z tach from the Junkyard and am planning on putting it in this weekend. Can someone enlighten me on how to wire up the tach. Thanks, Marcos Quote Link to comment Share on other sites More sharing options...
Hybrid240z Posted November 21, 2002 Share Posted November 21, 2002 Anyone have the correct wiring for the 280Z tach into the 240Z. I want to install it this weekend. Ground is the black wire...right? Is the green wire next to the black wire the tach wire? So what is the red wire with the black line? Is that a power wire, ignition wire????? That's all I need if anyone can help. Thanks, Marcos Quote Link to comment Share on other sites More sharing options...
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