LS2 tach problem

[m1noel]

I fired up my LS2/T56 for the first time Friday night. Everything is sweet except the tach. No needle movement whatsoever. Johns recalibrated it during the swap, there is power, but no rpm's. What to do?

Thanks for your input,

Mike

[VinhZXT]

Mike,

Have you verified that your tach was working before the swap? This is the only thing I can think off. I didn't go this route because of this reason. For the price of buying the converter and recalibrate the tach I could have bought the autometer gauges and it's a direct hook up. It worked great in my friend's swap. I might do the same on my Ls1 swap soon too. Good luck

Vinh

[Pop N Wood]

Mike,

Have you verified that your tach was working before the swap? This is the only thing I can think off. I didn't go this route because of this reason. For the price of buying the converter and recalibrate the tach I could have bought the autometer gauges and it's a direct hook up. It worked great in my friend's swap. I might do the same on my Ls1 swap soon too. Good luck

Vinh

 

By converter do you mean the speedo converter?

 

I thought the only thing required to "recalibrate" the tach was to turn one adjustment screw to the end of it's travel. At least that is what the JTR manual says, is it different for LS motors?

 

Also make sure you have a 280 tach and not a 240 tach, since the 240 units are current activated and, as per the JTR manual, will not work with the more modern tach drives (which I believe are voltage activated).

[VinhZXT]

Pop,

Yes the converter I mentioned is the electric to mechanical converter for the speedo. When I talk to JCI they said I had to send in the tach for recalibrating. It was a lot easier to use autometer gauges and that was what I used.

[m1noel]

Yes, the tach was working, and it is a 280 tach. I really wanted to keep the stock guages, just my preferance. The speedo converter works great though and was easy to hook up and calibrate. I just don't know if the tach signal out of the ECM will trigger the tach. Ulises had the same problem with the autometer tach, he had to hook it up to a coil I believe. There has to be a way.... My tach is back at JCI right now. I'll have to see what they say.

Mike

[VinhZXT]

For the autometer tach you have to set it in 4cyl mode. Don't ask me why. If you set it at 8 cyl mode it won't display correctly and it jumps all over the place. I heard from a guy on LS1tech that you can hook up a pull up resistor to eliminate the jumpings of the needle. I didn't do this on my friend's LS1 swap and the tach was OK. I used the tach signal coming from the LS1 Inline Harness so it might be coming from the PCM. Maybe there is something with the LS2.