Bouncy Tach
Thread Starter
Burning Brakes
Joined: May 2003
Posts: 990
Likes: 0
From: Germantown TN
Bouncy Tach
My tach has just recently decided to go crazy. When I punch it the tach starts bouncing around everywhere. If I slowly accelerate up to 2K rpms it wont do it anything but as soon as it gets higher then it starts bouncing really bad. What could be the problem? I'm lost on where to start. :confused:
Melting Slicks
Joined: Nov 1999
Posts: 2,372
Likes: 227
From: N Cal
Re: Bouncy Tach (ElectronBlueC3)
It could be either the tach drive gear or the cable. I would check the cable first to see that it has no sharp bends and turns smoothly in the housing. Good Luck.
:cheers:
:cheers:
Racer
Joined: Jul 2001
Posts: 260
Likes: 0
From: Ipswich, MA
Re: Bouncy Tach (l2vette)
It could be either the tach drive gear or the cable. I would check the cable first to see that it has no sharp bends and turns smoothly in the housing. Good Luck.
:cheers:
:cheers:
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Re: Bouncy Tach (l2vette)
My tach was doing funky things for a while. It would rev smooth to 2K, then start working back to 0, then back up again.
I traced the problem to the tach filter mounted on the intake manifold. I don't think my new fuel injection system and coil liked it much. Bypass yours and see if it works better.
I traced the problem to the tach filter mounted on the intake manifold. I don't think my new fuel injection system and coil liked it much. Bypass yours and see if it works better.
Thread Starter
Burning Brakes
Joined: May 2003
Posts: 990
Likes: 0
From: Germantown TN
Re: Bouncy Tach (BSeery)
Well I don't have any of the original motor in the car, so im still finding out where things are and what needs to be hooked up. I'll look for a tach filter if i can find one and maybe a crimp or two in the cable. Thanks for all the help guys! :yesnod:
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Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
Re: Bouncy Tach (ElectronBlueC3)
Could be the tach circuit board too. These are known for going bad after 20-25 years.
(along with most of the rest of the car too) :lolg:
Good Luck!
:seeya
(along with most of the rest of the car too) :lolg:
Good Luck!
:seeya
Le Mans Master
Joined: Mar 2002
Posts: 8,575
Likes: 3
From: On an island surrounded by sharks Hawaii
Re: Bouncy Tach (ElectronBlueC3)
Start with the tach filter and then the speedo/tach circuit board. Check this link
http://forums.corvetteforum.com/zerothread?id=647286
http://forums.corvetteforum.com/zerothread?id=647286
Melting Slicks
Joined: May 2003
Posts: 2,253
Likes: 1
From: Rochester Kent
Re: Bouncy Tach (DMONSVETTE)
My '81 does axactly the same as yours!! I think it is a faulty tach board, there is power going to it because it moves, but just like yours it is not working right at all!!! If you find anything different, I would appreciate the advice.
And by the way, when i got my '81 it wasn't working at all, i bought a tach board from a place in the UK and it does what yours does now. I spoke to some one in your country( i think it was called Redline Gauges or something like that) and he was very helpful and said he thinks it is a faulty tach board and explained there was a bunch manufactured that were in circulation that caused the exact problems mine was showing. :cheers:
Pro
Joined: May 2003
Posts: 601
Likes: 0
From: Nottingham
Re: Bouncy Tach (ElectronBlueC3)
A bouncy needle sounds more like you DON'T have a tach filter hooked up in the first place. Or you've got one, but the ground's bad. Follow the tach wire thru from the distributor, the filter's supposed to be bolted to the inlet manifold. Some people move them, but fail to keep them grounded by bolting them to something insulated. If it is missing, I'd try to get hold of one before you fry your board. There's a guy who makes new ones somewhere on the web, but they don't look original. Can't remember the site, but his name's Rodney Dickman.
The filter only contains a couple of resistors and caps, nothing too complex.
Good luck!
The filter only contains a couple of resistors and caps, nothing too complex.
Good luck!
Melting Slicks
Joined: May 2003
Posts: 2,253
Likes: 1
From: Rochester Kent
Re: Bouncy Tach (theoUK)
Theo, Mine did this with the tach filter in place and I was told to remove the tach filter. Alot of people have said that you can remove them with no problem. When i removed it, it made no difference. :confused:
Melting Slicks
Joined: May 2003
Posts: 2,253
Likes: 1
From: Rochester Kent
Re: Bouncy Tach (theoUK)
PaulD, Did you get my email??
Can I help you get your tach working properly again?
:cheers:
Can I help you get your tach working properly again?
:cheers:
Pro
Joined: May 2003
Posts: 601
Likes: 0
From: Nottingham
Re: Bouncy Tach (Pauld)
Cool, just let me know if you do want to try a new chip out. I have access to all the equipment needed to test the system, so we'll see what happens. I guess as long as it works (even if not quite right) then like you say, there are many many other things to be looking into. The joys owning a car that's pushing its quarter century!
(Hang on, I've just made my quarter century, and nothing's fallen off me yet!) Famous last words...
:cheers:
(Hang on, I've just made my quarter century, and nothing's fallen off me yet!) Famous last words...
:cheers:
