New ECU but still haveing problems
 

I just put the new ECU in, the car is running so much better. Tho my RPM gage still is not working. any ideas how i can fix my rpm gage on my 1986 rx7 sport 13b n/a?

tach not working? i believe its getting signal from one of the coils, check that your coils are all firing
if yes, then check all wiring related to Tach (as described in FSM)

i will try that out, thank you

Ohm out the YELLOW/BLUE wire at the Trail coil assy TO the back of the combination meter. If it ohms out, then you have a combination meter problem.

This is assuming that you already made sure the TRAIL coil plugs are firing. If they are not, then forget about ohming the YELLOW/BLUE wire out and find out why the TRAIL coil assy is not firing.

free fsm online

My tack wasn't working but neither were my gauges because the meter fuse was blown.

my speed gage works, and my car idols fine. so i whoud think my coils whoud be fine then. I will check the wireing.

The speedometer is purely mechanical.

A RX-7 will run just fine up from idle to redline with no Trail coil assy.

If the Trail coil assy is not working, it follows that the tachometer will not work. The tach signal is picked off the trail coil assy (if memory serves).

http://www.teamfc3s.org/info/articles/demystifying.html

The signal wire is colored YELLOW with a BLUE stripe on it. It can be found at the Trail coil plug.

Idle the car and while the car is idling, gently pull one of the two sparkplug wires out of the Trail coil. Just pull it out of the bore a sixteenth of and inch or so and tell us if the sparking isn't happening b/t the wire and the bore.

main relay
 

make sure that you afm is connected and the check your main relay and make sure its bolted on the car, you may want to get another on and try it.

i had the same problem, the car worked fine and the rpm would not work, and i found out that the main relay was loose.
so i hope that helps you

I hooked up battery backwards and I had a blown meter fuse. I replaced that and my car runs, and all the meter gauges work except for the tachometer. I measured the resistance on the trailing coils and they were both good. Using a voltmeter could I try measuring a voltage at the trailing coil tach hook-up and if I don't get anything that means there is a problem with the igniter or something and possible not the tachometer?