Tachometer sweeps to 8000 RPM

[jefflgalla]

Greetings to Fiat forum group,
I have purchased a 1981 Fiat Spider with 37K miles on it that sat for a period of time. The body is in very good condition; however, the sitting has resulted in some issues that I have to work out. I have replaced the gas tank, fuel pump, filter along with the injectors due a rusty tank and the car is running pretty smooth. One problem I am unable to figure out, is the tachometer sweeps to 8000 rpm when I turn the ignition on, and it remains at 8000 rpms once the engine is started. I am not sure where to begin to begin to figure out the issue with the tachometer. The forum has been a great site as I am new to owning a Spider, but always liked the looks of this vehicle. Thanks for those who know the ins and outs of the Spider.

[18Fiatsandcounting]

One problem I am unable to figure out, is the tachometer sweeps to 8000 rpm when I turn the ignition on, and it remains at 8000 rpms once the engine is started.

That sounds to me like the signal wire for the tachometer (brown/white as I recall) is not connected to the right place. It should be connected to the opposite terminal on the coil from where the pink wire is connected.

Another (less likely) possibility is that the wiring behind the dash for the tachometer is messed up.

-Bryan

[jefflgalla]

Thanks for the information. Will check out today with the wiring locations and post results.

[jefflgalla]

Looked at wiring as suggested to coil and it is correct. One of posts also mentioned about the pick-up wires inside the distributor getting frayed. I checked the wiring inside the distributor which the wires to the pick-up were frayed and partially broken. I am thinking this is the problem to the tachometer. I have ordered a new pick-up and will update once installed. Thanks for the assistance!

[18Fiatsandcounting]

I checked the wiring inside the distributor which the wires to the pick-up were frayed and partially broken. I am thinking this is the problem to the tachometer.

Yes, this is likely the issue. It doesn't explain why the tach would go to 8000 when the ignition is turned on but before the engine is started, but maybe we're about to learn something here. Let us know what you find out.

-Bryan

[jefflgalla]

Update, replaced distributor pick up with new aftermarket from Vick Auto Sports and the car is running fine. It did not take care of the tachometer problem; it still sweeps to 8000 with ignition turned on and stays at that position with the engine running. The wiring from the coil is correct. I have also detached the coil wire for the tachometer with just the ignition turned on and it still sweeps to 8000 rpm. Obviously, it is getting power from a source it should not be getting power. I see in the posts that the ignition switch causes some electrical issues, is this a possibility? All the other gauges are working properly. Any suggestions where to go from here?

[18Fiatsandcounting]

A capacitor placed inline with the brown wire might solve the problem. See this post:

http://www.fiatspider.com/f15/viewtopic ... or#p306629

-Bryan

[jefflgalla]

Note, replaced the tachometer with a used one from ebay, that solved the issue with the full sweep so the tachometer must have a broken spring internally. Thanks for the posts