Tachiometric Switch - what is it?

[donerehart]

I have a 76 spider and I am told it needs a tachiometric switch. What is it and why is it necessary?
Thanks,
Don

[Fi8spider]

Tachymetric switch, My only run in with one was when I ripped it out to fit my twin 40 webs, but basically I had to work out what it did before I did so.
Its part of the cumbersome SMOG system bogging these beautiful engines down. I could rattle on about it but basically it regulates or more so governs if your fast idle valve is activated or your idle stop is activated. Its determining signal is sent by the cluch and gear selection switches. You would most probably need it for correct idle on the smog system.

[ventura ace]

I believe that it's a safety device that cuts power to the fuel pump after 'X' number of seconds after the engine stops running. The purpose is to eliminate the flow of fuel in case of an accident (for cars with electric fuel pumps).

Alvon

[Fi8spider]

Hence the pick up signal from the coil. Makes sense ace.

[donerehart]

Mark - if you check this...did you leave it on your 76?

[ventura ace]

I believe that it's a safety device that cuts power to the fuel pump after 'X' number of seconds after the engine stops running. The purpose is to eliminate the flow of fuel in case of an accident (for cars with electric fuel pumps).

Alvon

I could be wrong on my guess about the fuel shut off. I see that you posted the same question on Fiatspiders.com, and received some replies relating the switch to the dual points in the distributor. Check Fiatspiders.com to read more -- fairly complete reply there.

Alvon

[donerehart]

Thanks everyone - as always you are an amazingly helpful group! Much appreciated. Hope to have car out of the shop this coming week after over 8 months... If it ever quits snowing here in St. Louis!