Crazy Tach

[12secondSY]

I now have GM TURBOs old ty and took it out this weekend. I noticed the tach works fine until I'm on it and up in the rpm at which point it starts going all over the place. Anyone had this happen? Why is it pissed off?
Just had the distributor out but everything back there seems good and I don't know if it did this before or not.

 

[bezerk]

Re: Crazy Tach

check your grounds

 

[Stangbeater]

Re: Crazy Tach

Also check you spark plug wires. Might be the arcing to the manifods. I had this problem with my wires, changed the wires and it went away.

 

[dgoodhue]

Re: Crazy Tach

The condition is commonly called Tach flutter, it usually cap/rotor, wires and plugs. I have also seen it to two wire connector going from the coil to the ditributor, I supose it could the coil or even distributor.

 

[blk00z28]

Re: Crazy Tach

The condition is commonly called Tach flutter, it usually cap/rotor, wires and plugs. I have also seen it to two wire connector going from the coil to the ditributor, I supose it could the coil or even distributor.

See, it just goes to show you, no matter the problem in these trucks. Cap, rotor, wires and plugs will always fix it. :lol:

 

[Crimson93Ty]

Re: Crazy Tach

If you ever have the cluster out to fix the oil pressure gauge needle flop fix, check your tach. Set it on the table so that the top of the cluster is slightly elevated. Take the tach needle and rotate it around about 1/2 way and then release it. It should have a cushioned drop back down to the bottoming peg that sticks out. If it just wildly drops and bounces off of the peg, congratulations, you have another factory fubared tachometer. I used a tach out of a 3.1 liter v6 sunbird to fix mine.

Hopefully plugs and wires fix your problem. If it does, it's where your ignition is breaking up under boost.

 

[Jimmy]

Re: Crazy Tach

Might be the pump for the alky injection.Ask Dave.

 

[Crimson93Ty]

Re: Crazy Tach

Are you talking about the capacitor? Seems like there was a fix for that issue that came out. There was a capacitor that went on there to prevent feedback. Here's a quote:

Regarding the tach flutter, I know with the SMC alky pump, noise would make it's way back into the ignition circuit and cause this behavior. To solve that problem, I just used a 220uF eletrolytic capacitor (# 272-1017) on the IGN feed wire for the SMC pump. I'll try unhooking the "ignition on" wire from the VSC tomorrow and plugging it into 12v hot on the firewall. If the tach flutter goes away, then I'll just reuse that cap I had on the SMC pump.

Maybe that will help.

 

[RSpengler]

Re: Crazy Tach

See, it just goes to show you, no matter the problem in these trucks. Cap, rotor, wires and plugs will always fix it. :lol:

Hahahahaha! You haven't read my thread... :rotf:
J/K
Rob

 

[QUICK STORM]

Re: Crazy Tach

I now have GM TURBOs old ty and took it out this weekend. I noticed the tach works fine until I'm on it and up in the rpm at which point it starts going all over the place. Anyone had this happen? Why is it pissed off?
Just had the distributor out but everything back there seems good and I don't know if it did this before or not.

time to update your sig.

 

[12secondSY]

Re: Crazy Tach

I'll check into the plug wires, they look almost brand new and are taylors i think. I'm pretty sure dave had done those recently though, how would the alky pump affect it? I haven't messed with any of that at all. I'll ask him if he knows when it started.
Going to change my sig too.

 

[blk00z28]

Re: Crazy Tach

I also want to know about the alky pump causing problems.. ???

I read the above and it says the noise makes its way back up.. How is this if my IC pump makes more noise then the alky one??

 

[GM TURBO]

Re: Crazy Tach

I'll reply here also...

Widen the plug gap a touch - I think I had them at .030 before the Nats and it was running well up to that point.

Also, either turn the alky off - or lower the pump speed. I turned it up when the outside temps were high and it that's when it got bad. You can turn the alky off - make sure all the ignition stuff is straight (everything has +/- 2K miles).

 

[Crimson93Ty]

Re: Crazy Tach

The noise isn't referring to the pump audible noise. We're talking about EMI noise and the capacitor placed on the 12 volt ignition that feeds the pump takes care of it.