I installed a new $400 tach (called a rally pack) on a '66 'stang. it never worked right. goes to 1500 & stops. i later realized it had a G.M. HEI ign. system. i know the old ford system works off the positive side of the coil (unlike any other systems). does any one know a solution to this mismatch?
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1981 Corvette has an electical tachometer that is driven by impulses from the distributor. First, check for blown fuses, next make sure the tach wire is plugged into the distributor. Next bypass silver tach filter or capacitor located by manifold to see if the tach moves at all. If these steps do not reveal a change in tach operation, then the most obvious next step is to remove the tachometer and get a new board for the tachometer. Unscrew and remove cluster lens and then unscrew tach bezel, and gently pull out the tach noting position of insulators. I believe these boards are available still at local autoparts locations. Replace board, note position of insulators and reinstall tach, bezel and lens. Old corvette are cool and are pretty easy to work on! Should be fixed, enjoy!
Sounds like the tach is either bad and should be replaced or there is a short or loose connection to or from it. Check the wires in and out of it. If it's in the dash, though, it won't be easy to get to. Good luck.
easy... remove the mechanical tach and fit the light from the old one to the new eletric tach. Next run a wire from the back of the tach connection that looks like a small pole and run that to your ignition coil - negative side. Also make sure the ground wire (black) is mounted to one of the install bracket posts that hold the tach in place behind the dash.
You check the right firing order? 1991 Ford Mustang2.3 liter SOHC L4
1991 Ford Mustang5.0 liter V-8 HO
Also, need check the PCM for someone short; sometimes this is the reason it wasn't sending a signal to the coil. You have constant
power at the coil but the ground signal doesn't fluctuate from on to
off while the engine is cranking. If the hall effects
switch in the distributor is bad it won't tell the PCM when to fire the
coil and the hall effect switch also operates the tachometer. So if
this switch is bad the tach and the coil would not work.
You have two sensors on the engine that send a signal to the computer, speedo, and tach. If just one of these sensors goes bad your speedometer and tachometer can just stop working. Check if these sensors are blocked or if broken then replace.