80 - odd problem with tach
Drifting
Joined: Dec 2017
Posts: 1,302
Likes: 226
From: PA
I'd start by just flexing the wire with the engine running and see if this causes the effect. If so, then you can clean up the contact (both wire and tach side) or crimp a new contact onto the wire if it's in the crimp.
Note that it may also be the same issue with the connection to the tach inside the distributor.
Last edited by vince vette 2; Feb 12, 2020 at 01:08 PM.
Thread Starter
Racer
Joined: Sep 2013
Posts: 331
Likes: 29
From: Moyock NC
A SWAG here. Since the tach is just counting electrical pulses, if it loses a some pulses it will read lower. It's possible the tach output contact at the distributor has corroded over the years. Under acceleration the engine will torque somewhat. Perhaps it's causing some movement in the tach lead wire causing the contact at the distributor to intermittently move onto an area with corrosion and lose some pulses. Also, if the contact crimp has deteriorated over time with corrosion inside, the same effect could result.
I'd start by just flexing the wire with the engine running and see if this causes the effect. If so, then you can clean up the contact (both wire and tach side) or crimp a new contact onto the wire if it's in the crimp.
Note that it may also be the same issue with the connection to the tach inside the distributor.
I'd start by just flexing the wire with the engine running and see if this causes the effect. If so, then you can clean up the contact (both wire and tach side) or crimp a new contact onto the wire if it's in the crimp.
Note that it may also be the same issue with the connection to the tach inside the distributor.
Drifting
Joined: Dec 2017
Posts: 1,302
Likes: 226
From: PA
Let me know when you find out. I like to know my batting average.
I've noticed that the tach on my '80, owned since new, sometimes just drops to 0. Likely a similar issue, but I have lots of more pressing concerns in the car.
I've noticed that the tach on my '80, owned since new, sometimes just drops to 0. Likely a similar issue, but I have lots of more pressing concerns in the car.
