can not get tack working with msd 8910?

[kully 560]

I have a early 1974 260 z with msd 6a ,8910 , blaster 2 coil ,e12/80 dissy.I hooked up the dissy ,msd 6a and engine runs great. but I can not get the tack working! unplug the harness from the ballast resister and was left with 3 wires in the plug . black /white tracer,blue solid,black /blue tracer. there was a seperate 12volt wire in with the harness that I used for the 12volt switch feed,black with white tracer. I believe the blue wire runs my tack, when I hooked up the blue wire with just the coil and e12/80 on the neg. side tack would jump around. so I installed several resistors in line trying to get the tack working with no luck. so I went with msd equipment. still can not get my tack to work. I have the msd 8910 and tied the blue wire in with the white wire from c term. on e12/80 and car will not start. any solutions thanks kurt

[Zforce]

Try this

[kully 560]

thanks zforce but I have that diagram and my wire colors are different .I have a bk/wh color, blue solid color ,bk/blue color. I spoke to msd several times today each tech tells me a little different but all say at the end I only need the single tach wire which I think is the blue .one tech said to try the diode but still no good and then several techs said to order the 8920 tach adaptor???they can not get it straight.

[beezee]

Wire connections for the 4 wire tach adapter , black to ground, red to 12v switched power from key( black with white tracer) and MSD small red,white to MSD tach output terminal ,violet to blue factory tach wire

[beezee]

Kurt ,the wire connections above is for the 8920 tach adapter and works in my 260 but I,m using the earlier mag pickup dizzy. I had the 8910 adapter when I was using the points dizzy.

[kully 560]

thanks for the help I will pickup the 8920 it easyer to do this then change the tach kurt

[beezee]

Kurt, Did the tach work before the ignition upgrade? Looking at old msd 6 literature the

Datsun- Hitachi electronic module connects the same as the points dizzy, the trigger white wire from the msd to the electronic module "C", 8910 tach adapter and the blue tach wire.Z-force wire diagram appears correct to the info I have. The tach is also fused and an inline resistor in the blue wire up in the passenger side footwell near where the main harness passes through the firewall.

[kully 560]

the tach stop working last summer when I installed the e 12/80 dissy. my 260 had the electronic dual pickup dissy in it which was the one for automatic cars. it retards timming when motor was warmed up for the emmissions crap back then. I tried several resisters in line with the blue wire but the tack just jumped aroung.thought I was close when I installed a 1 watt 7.5k ohm resister in line but then it was still never right. so that why I went with the msd .all I can say is the msd is worth every penny as far as the car runs big improvement .msd says the 8920 has a seperate wire just for the tach lead .they claim the current is to high for the 8910. but I see alot of people here use the 8910 . I read alot of posts and it looks like alot of 240 cars update with this msd and maybe the 240 tachs are different that I do not know kurt

[beezee]

The 260 tach is a voltage triggered tach using coil (-) as a trigger. Earlier 240,s I believe use a current triggered tach by use of coil (+) ,not sure of years?

[kully 560]

yes, I believe that msd told me that the 8910 is for positive side of coil and the 8920 is for the neg. side of coil . I ordered the 8920 so when it gets here I will give it a try, hope it works . it bothers me to have a good ingition now and no tach.i could install the autometer tach but it does not look like the orignal guages close but no cigar kurt