Spikey Tach Video

[Johnny P]

Tach needle spikes all over only while cranking. Once the car starts it works fine. Wires under dash appear fine, all other gauges also working fine. I also notice when I turn key on (not starting) the rpm needle will give a small jump and when shutting car off the needle also bounces around below 0 rpm then back up and resting at 0 rpm. I attached a video file showing how it cranks.
Anyone know what the problem may be???

Thanks

[URL=http://s371.photobucket.com/albums/oo159/johnfiveo/?action=view&current=Bouncingtach2.flv] View attachment 297078 [/URL]

 

[JohnnyRebel]

That's not too bad. Mine will bounce all over the place when I'm driving down the road and somtimes go up to the redline on its own and stay there for a few minutes. Doesn't happen everytime I drive it but I think these cars have tach problems from the factory and are not all that accurate, most of the time you see people with aftermarket tachs mounted in their foxes - for good reason i think.

 

[LiquidGT]

Mine did that as soon as I put an Accel TFI module on; then it crapped out. So I'm using a Wells module and I noticed that the tach acts normal on start up now.

I think part of the tach circuit goes through the module; from my experience it could be that.

 

[Johnny P]

Yes, one does go to TFI. Think I will try replacing TFI and hope problem solved.
Thanks for the replies