Tachometer on a 1959 Replica Porsche 1966 912 engine

Poor ground? Is it a mechanical drive off the oil pump? Broken/breaking cable?

That should not be a mechanical tach.  I suspect either a poor connection between the coil and the tach, or a bad tach.

Many years ago I had that happen with that same tach. Final solution was recurring points "bounce." I finally solved it by converting to a Petronix points replacement setup. Is the distributer a "009"?

I had same points bouncing issue on 914 and it took new points (didn't now about Petronix back then).  I had a '63 356 and the tach was cable drive off bottom of distributor.

Wolfgang, thanks for the reply. I already have the Petronius set up and had a problem before with them, they told me to change the regulator and make sure ignition wires were good. All that done, and now tech is doing it all over again, it is a 050 Dist. If that helps

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> On Mar 5, 2017, at 10:04 PM, SpeedsterOwners.com <**************> wrote:
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Hello, thanks for the reply, I already had converted to Petronius setup and it's an 050 distributor.

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> On Mar 5, 2017, at 9:10 PM, SpeedsterOwners.com <**************> wrote:
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Hi Dean,

we had a simular problem here in our forum in Germany. 

It really seams that some of the RPM tachs don´t work with some electronic ignition systems. But ther might be a simple way to solve the problem:

You just put a simple "power" diode inline in the cable from the ignition to the tach. That "cleans" the signal.

Here it worked perfect

 

Best Jan

http://forums.pelicanparts.com...2-bouncing-tach.html

 

Thanks, I will try and clean, and call VDO, they might have a resistor fix on their end.

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> On Mar 6, 2017, at 9:54 AM, SpeedsterOwners.com <**************> wrote:
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Wolfgang, thanks for the information, I put a resistor in the line on neg. side of ignition coil and so far good. Thanks again

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> On Mar 6, 2017, at 9:54 AM, SpeedsterOwners.com <**************> wrote:
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Jan, thanks for the information, I put in resistor on neg side of coil and so far so good. Thanks again

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> On Mar 5, 2017, at 11:45 PM, SpeedsterOwners.com <**************> wrote:
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Hello, thanks for the information, a resistor on the neg side of ignition coil seems to work so far. Thanks

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> On Mar 5, 2017, at 9:10 PM, SpeedsterOwners.com <**************> wrote:
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didn't know that a simple resistor also works.

good to know!