Aftermarket tach issues

[CarRacer]

I'm trying to run an aftermarket tach and it's not receiving a signal. I'm tapping into wire 109 on the ECU and the tach doesn't move.


Can I tap directly into the wire on the igniter or elsewhere to get a signal? This is for the motor swap I'm doing so there isn't a body harness and I can tap into the engine harness where ever I want to run new wires.

Thanks.

 

[curtis]

Should be a tach signal on the ignitor but I think you have to buy a tach interface/adapter box for a distributorless ignition. MSD/autometer/Accel all sell them. Look on ebay here click me

 

[Andy_S]

Quoting CarRacer:
I'm trying to run an aftermarket tach and it's not receiving a signal. I'm tapping into wire 109 on the ECU and the tach doesn't move.


Can I tap directly into the wire on the igniter or elsewhere to get a signal? This is for the motor swap I'm doing so there isn't a body harness and I can tap into the engine harness where ever I want to run new wires.

Thanks.



pin 109 is the tach output from the igniter. Do you have miss-matches 90 and 91-94 components?

 

[CarRacer]

It's all 91 stuff from my galant.

Now, it's just an el cheapo Auto Meter "AutoGage" series tach. We ran it on the stock Chevette 1.6 which uses a distributor. Is there a big difference between the tach signal from the VR4 ECU and the negative post of the ignition coil? I'm going to check the ECU wire with a multimeter next and verify that there's a signal there.

 

[Andy_S]

Any update? I'm currently working on a similar problem.

 

[kama1]

I tapped mine on the tach pin on the igniter when i was running an autometer.

 

[pot]

I used the following diagram for referencing the RPM signal when installing my HKS turbo timer and Greddy-e01 Profec. The "I" port on the harness side has worked for me on both occasions. I would "assume" this should work for you.

 

[CarRacer]

Quoting Andy_S:
Any update? I'm currently working on a similar problem.



I ended up splicing into one of the + feed wires on the coil pack. The tach only read half as it was only getting a signal from two of the four the coils. The igniter wire is out as it's a 5v signal and the Autometer tach is looking for 12v. An aftermarket signal converter like Curtis mentioned seems to be the best solution there but not a cheap one as they're ~ $90 from Summit. I don't give a sh*t that it only reads half though so we're running it like it is, this isn't a street car and nobody but us will drive it.

 

[Andy_S]

Thanks CarRacer. Actually, you might be able to get the tach to read right by splicing into two coils and using diodes to prevent them from cross feeding each other. I also had a problem with the 5v signal because the factory tach in my car (non-mitsu as well) was looking for 20v. I believe scaling the input resistor may allow it to work properly with the 5v signal.