1981 tach not working

[Keith G.]

What is the first thing that goes wrong on a 81 tack, where do I start????

[David H.]

Re: 1981 tack not working

Keith,

Ground - First thing to check. Next would be connection at distributor.

Dave

[Tom R.]

Re: 1981 tack not working

What is the first thing that goes wrong on a 81 tack, where do I start????

After the easy stuff, target the tach board. It's said that 90% of the time the culprit is the tach board. Those originals used think copper paths that burned out over time and components not as stealthy as those today. Below is link to an article written probably ten years ago and has relevance today. To replace in an 81 is easy compared to a 75-77 where the dash has to be removed. I've replaced a couple.

http://hunt4cleanair.net/Articles/tachboards.pdf

[David H.]

Re: 1981 tack not working

Keith,

I believe your 1981 uses a computer (ecm) controlled carburetor. ECM receives a tachometer signal as one data input. Is that system still functioning?

Dave

[Joe L.]

Re: 1981 tach not working

What is the first thing that goes wrong on a 81 tack, where do I start????

Keith-----

It could also be the tach filter. These are also well known for failure. It was GM #14020025 but it's long-since GM-discontinued. I don't know of a replacement source but there may be one by now.

[Keith G.]

Re: 1981 tach not working

Keith-----

It could also be the tach filter. These are also well known for failure. It was GM #14020025 but it's long-since GM-discontinued. I don't know of a replacement source but there may be one by now.

John, paragon said to try to by-pass the filter, so I did, didn't fix it, but did wake it up. It was stuck on 1200, now when I turn the key on it goes to 0, with the motor at idle it goes to 750, give it some gas and it will slowly make it's way to the right RPMs, back off and it goes back to the 1200 at idle (which is wrong), tap on the dash and then it goes to 750.??????

[David H.]

Re: 1981 tach not working

Keith,

You might find some useful information in link below with connections.

http://repairs.willcoxcorvette.com/category/tach/

Dave

[Tom R.]

Re: 1981 tach not working

John, paragon said to try to by-pass the filter, so I did, didn't fix it, but did wake it up. It was stuck on 1200, now when I turn the key on it goes to 0, with the motor at idle it goes to 750, give it some gas and it will slowly make it's way to the right RPMs, back off and it goes back to the 1200 at idle (which is wrong), tap on the dash and then it goes to 750.??????

Tach board!

[Joe L.]

Re: 1981 tach not working

Tach board!

Tom and Keith------


GM #25023527. Discontinued but reproductions are available.

[Tom R.]

Re: 1981 tach not working

Tom and Keith------


GM #25023527. Discontinued but reproductions are available.

Yeah...I tested one for Wilcox (made in USA) who reproduces those with new components and better than what was coming out of China! My Pace Car has a Wilcox in it.