Trying to wire HEI distributor to factory tach harness, i have spliced into white wire that hanes manual says is the tach signal from ignition coil. When the wire is connected, there is no spark, tach in the dash or no tach, only way to get spark back is disconnecting tac wire from distributor. help please

 

Large cap or small cap? I've seen green as a tach color. Where are you grabbing the white wire?

 

It's obviously the wrong wire.
And why don't people ever say what year their car is when they ask tech questions???...

 

The tach wire is actually supposed to connect to the side of the coil primary that goes to the points or the ICM output. (same functional thing; just, different ways of getting there) If it's grounded, then it creates a condition just like the points don't open (or the ECM switch from conducting to not). If you've ever had one of those lawn mowers with the little switch that operates when you push the throttle to "stop", it's the same thing.

Either you have the wrong white wire (not likely), or there's something wrong with the tach circuit. Just the same, there's no reason whatsoever to "splice" anything, so, that part is a bit scary.

Follow the wire back toward the firewall. There may be a metal cylindrical object with a wire coming out of each end, one of which is ... that white wire. It's a filter for radio interference. It can go bad by becoming a short to ground. Try unhooking the wire from the other end of the filter, and plugging that one, the one that comes out of the harness, into the dist instead, and see if the engine runs. If so then the filter is bad.

 

Will refer to this if/when i go back to factory tach, but for the time being i just undid the wire i spliced into the tach harness and covered it up, then ran an aftermarket bosch tach and that works great.
1982 camaro z28 with a 400sbc swap.

I do have one more question however, it sounds like a damn geiger counter under my dash, anyone have any idea what this could be

 

Could be a relay, such as the Choke heater relay...

 

Edit definitely a relay, It's whatever this one here with two brown one blue is, 82z28 going to do some research and try and figure it out but any thoughts appreciated as always

Edit 2: it was this green thing which I believe to be the computer carb relay and since I have hei and electric choke wired separate it was just getting random signal and actuating rapidly, unplugged it while it was running and nothing happened, shut off the car and started back up fine. Going to wait for it to cool all the way down and start up to see if anything if off but if not I think I can finally start putting my cluster/lower dash back together.

The relay , part numbers visible

F in the bottom corner

3 prong relay

Where it was in the relay block, removed the chime to get access but I think I'm going to swap it with something else I have a few in the garage


1Blue 2brown wire, I can feel the relay on top and feel the clicking from that

 

That's the Choke heater relay. With it removed, your "Choke" (alternator) light will be on ...