'91 tachometer
Thread Starter
Instructor
Joined: Jun 2005
Posts: 193
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From: woodinville washington
'91 tachometer
the tach in my '91 skyrockets when the motor is running, even at idle, but with the ignition on but the motor not running the tach is at zero, and when i disconnect the tach wire from the distributer the tach remains at zero even when engine running.
is there something between the distributer and my tach that could be causing this? like a tach module or something?
is there something between the distributer and my tach that could be causing this? like a tach module or something?
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
Sounds like the tach filter problem. It's bolted to the back of the DS head and looks like a capacitor from an old school ignition system. My understanding is that it is a discontinued part.
Instructor
Joined: Apr 2002
Posts: 223
Likes: 0
From: Spokane Wa
Tach filter.
Does this need to be grounded to be accurate. Noticed my tach was bouncing since I rebuilt the motor last month. Saw just last night that I had not bolted this down. It is secure now but I have not started the motor since doing this. :o
Drifting
Joined: Apr 2005
Posts: 1,445
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From: Robert Lee Texas
St. Jude Donor '05-'06
Originally Posted by Steel Blue 91
Sounds like the tach filter problem. It's bolted to the back of the DS head and looks like a capacitor from an old school ignition system. My understanding is that it is a discontinued part.
Burning Brakes
Joined: Apr 2000
Posts: 980
Likes: 2
From: Chandler AZ
Yellow,
I am betting on filter problems also. They can, once in a GREAT while be found on the Forum in the for sale area.
YES!!! and make sure the ground is good and tight. My 90 had a similar issue. It was just Mr. Filter had a loose ground. When I would stomp the gas it would flake.
I am betting on filter problems also. They can, once in a GREAT while be found on the Forum in the for sale area.
Originally Posted by fnseeker
Does this need to be grounded to be accurate. Noticed my tach was bouncing since I rebuilt the motor last month. Saw just last night that I had not bolted this down. It is secure now but I have not started the motor since doing this. :o
YES!!! and make sure the ground is good and tight. My 90 had a similar issue. It was just Mr. Filter had a loose ground. When I would stomp the gas it would flake.
Thread Starter
Instructor
Joined: Jun 2005
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From: woodinville washington
Originally Posted by VAHROOM
Yellow,
YES!!! and make sure the ground is good and tight. My 90 had a similar issue. It was just Mr. Filter had a loose ground.
YES!!! and make sure the ground is good and tight. My 90 had a similar issue. It was just Mr. Filter had a loose ground.
Instructor
Joined: Aug 2004
Posts: 108
Likes: 0
Originally Posted by yellow dragon
thanks, since im pretty much going by feel back behind the head, can you tell me where the filter is grounded?
I had the exact same problem with my 91. I built my own filter and that fixed the bouncing tach. Hope this helps!
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Racer
Joined: May 2005
Posts: 372
Likes: 17
From: Cape Coral, FL
Originally Posted by yellow dragon
thanks for the help, i pulled the filter and im in the proces of making my own.
Thanks!
JTK
Thread Starter
Instructor
Joined: Jun 2005
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From: woodinville washington
Originally Posted by SOF Vette
I have this EXACT problem, can you enlighten me on how you build your own filter???
Racer
Joined: May 2005
Posts: 372
Likes: 17
From: Cape Coral, FL
Originally Posted by yellow dragon
im not sure yet, ill probably just take it apart and copy whatevers in there, i guess the filter just lowers the power sent to the guages so that you dont burn out the guage cluster, so im hoping there's just some resisters in there, but ill keep you posted
JTK
Intermediate
Joined: Jul 2004
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Originally Posted by yellow dragon
im not sure yet, ill probably just take it apart and copy whatevers in there, i guess the filter just lowers the power sent to the guages so that you dont burn out the guage cluster, so im hoping there's just some resisters in there, but ill keep you posted
Instructor
Joined: Aug 2004
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Originally Posted by SOF Vette
I have this EXACT problem, can you enlighten me on how you build your own filter???
90-91 tach filter spec
I´ve been using this filter in my Vette some time now and it works really well.
As you can see I only managed to measure one out of four components in my stock filter, do you manage to measure more, please let me know.