cylinder setting when pulling tach signal from coil

[protour_chevelle]

Hey guys, I'm wondering what cylinder count I would set my tach on when pulling the signal from a coil? I'm having a hard time getting it. My tach just bounces around 1k rpm and steady's out when revving. But doesn't go higher then 1.5k rpm?

Thanks in advance.

[Mike Norris]

If you are pulling off the coil signal, you need to be set on a one cylinder configuration. There are not many tachs with a one cylinder setting as most use four, six or eight configurations. If you are using a stock LSx PCM and decide to use the tach, or engine speed signal for the gauge cluster out of the PCM, then you need to use a four cylinder setting. Hope this helps.

Mike Norris

[protour_chevelle]

See thats the thing. I'm not getting any signal from my white engine speed signal wire so I was just going to run off a coil.

[Ron S]

I've done quite a few of the conversions,I've had to set the Auto Meter tacs to the six cylinder setting to get them to work right.Some have told me they used the four cylinder setting.But I've always used the white tac feed wire from the PCM.Do you have any ideas why there is no feed out.Did you do the harness ,or is it an after market one?I have all the pin outs for all the different year PCM's if you want to be sure its in the correct spot,and possibly doesn't have a broken wire.Ron

[19topless69]

I'm having the same problems with my autometer tach . Set it
on the 4cyl mode and hooked it up to the white wire coming out
of the pcm(speartech harness) and nothing. Called Autometer
and they said it 's very common that there tach's don't work
with Ls1/2 computers.He said something about the computer only
puts out a pulsating 5volt signal and there tachs have to be adj
to work on that voltage . They would do this free of charge, just
have to ship it to them. Sucks because my entire dash has to come
out!

[Ron S]

The last one I did was there new cobalt series,they said it had to be hooked up on the 4 cyl setting,but it only worked right on the 6 cyl setting,I've done several with there cheap tacs,with no problems,and am getting ready to wire and hook up the one in my camaro.I'm using the Ultra Lite series in it,I guess we'll see.I did the engine harnesses on all of them myself and used the factory tac feed,I'm sure thats the samething Speartec uses? GM feeds the coil hot anytime the key is on and pulses the ground to energize the coils,I really don't know how you would hook them up without the white tac wire.Ron

[nitrovette]

i too am having the same trouble with my autometer phantom tach,ive tried 4 cyl and 8 cyl ,ill have to go back and try it on 6 cyl again.Im using the white a10 wire too from pcm.I was told recently about sending it back to autometer but its a pain to get my tach out,i just had my speedo out to fix that last week.

[Phillip_L]

What PCM are you guys using. I am using a 1999 PCM and hooked into the white wire on Pin #10 (Red Side). Shift light and tach work fine.

[nitrovette]

im using the 99 pcm also,hmmm weird some guys have trouble some dont.

[nitrovette]

My brother came over today and put his efi live on it and checked the tach setting and its set at a value of 6,which i believe is stock right?

[nitrovette]

Well i got efilive and this morning made a change in tach output from 6 to a 4 and loaded that in and now my autometer tach finally works.Took it out for a good run bounced it off the rev limiter a few times at 6200 and came home.Finally it works right.