Erratic tach

[roman.lysiak]

So I’ve got the car back on the road. Running nice for the better part. changed the wires to IE performance and swapped out the internals of the IE distributor for mech advance tii with the hot spark. It still has a slight hesitation here and there with the tach jumping around especially when engine is revving 4K plus.

 

Is there a ground somewhere to look at to trouble shoot this behaviour. Coil and ballast have all been checked with ohm meter and check out.

 

Roman

 

 

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[Schnellvintage]

I have seen wires frayed or corroded internally hidden beneath the insulation.  This would cause your issue, also check the wiring behind the instrument cluster.  Sounds like your on the right track. 

Hope this helps a little.

Matt

[AustrianVespaGuy]

I think almost for sure this is an issue with either the points gap being a bit small or a shot condenser that's allowing the points to arc some.  Classic symptoms when the car runs OK in the lower revs but then stumbles/misses and you lose tach signal intermittently as the revs climb a bit.

[roman.lysiak]

No points or condenser. Put in that hot spark unit. Will check for loose wires behind instrument cluster when kids go to bed.


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[JsnPpp]

Check that the hot spark wires in the distributor (black and red) are not rubbing against the magnetic pickup and have worn through, possibly causing noise or even shorting.

 

I've been here before but cannot remember the fix. As SchnellVintage said too, check all grounds and general connectors.

 

For grins can also put the old spark plug wires back and see if the problem changes.

 

Jason

[visionaut]

Not sure of Hot Spark, but with a PerTronix dizzy setup you need to also run a Tach Adapter to have a non-erratic tach.

['76mintgrün'02]

20 minutes ago, visionaut said:

with a PerTronix dizzy setup you need to also run a Tach Adapter to have a non-erratic tach.

 

I don't think I've read that suggestion before... unless it is being used with MSD ignition.

 

I could be wrong though... I use points and a condenser.

Tom

[visionaut]

5 minutes ago, '76mintgrün'02 said:

 

I don't think I've read that suggestion before... unless it is being used with MSD ignition.

 

I could be wrong though... I use points and a condenser.

Tom

Yeah Tom, you’re right. I had a brainfarht.  The tach adapter is for the MSD...

 

Tom