Does anyone know how to wire up the tach or how these things work?

The truck originally had an EFI 302 with m5od. The pushrods were bent by previous owner and I got a screamin deal on a mercruiser 351 small block. The motor is an 86 with a 4 barrel carb. I have an MSD blaster 2 coil on it and the dizzy is a presto lite with mechanic/electric advance.

I would like to have a working tach... I looked at a wire diagram in a haynes book and tried hooking the ground wire for the tach to ground and the other to the hot side of the coil but it did not work. I'm horrible with wiring, I don't understand diagrams real well... and I'm assuming that the tach runs off the ecu...

Any help would be appreciated, thanks... greg

 

If you are using the same ECU, then it should be plug and play

 

Uh... I removed all EFI stuff from under the hood... It has a carb, with a mechanical fuel pump, and an old points distributor that was updated with electric ignition guts...

The computer is still in the truck, but all the wires are gone... I cut the wires for the temp sensor, oil pressure gauge, AC and coil out of the harness and through the rest out...

The dizzy has 2 wires, hot and ground that go to the coil, and the coil has one hot accessory wire going to it... Stock ignition is gone... I wish I would have thought of the tach before I got this far... lol

 

The 4 wires to the tach on a 96 are
Black = ground
Black/Yellow = 6/8 select, which is grounded on a V-8 and open on a 6
Red/Yellow = 12V hot in start or run
White/pink = cold side of coil

your truck should be similar

 

The tach has nothing to do with the EEC or ignition module; it runs off battery power & 1 wire to the coil (-). A stock tach cluster would be the easiest & best-looking because it's PnP. If you can't find one at a local JY, e-mail me thru my SMN profile or my profile here about this one:



If you want to use an aftermarket tach, all the wiring you need is at the stock cluster connector - you don't need to pull any wires thru the firewall.

 

awesome... thanks guys... one last question... Are these wires the same color on the chassis' connectors before it plugs into the engine's harness? Or do they change color in between there and the cluster?

 

awesome.. tach works... thanks guys