Still trying to get tach working

[stevef]

I’m still struggling to get my tach working. I installed my 2.2 in my 71T. It has a Marelli distributor. The black and purple lead is connected to the contact on the side on the distributor and leads into the RPM transducer on the rear electrical panel. I know I have continuity to the tach. Since the car is a collection of bits from various cars I don’t know if everything matches. I’m not sure if the RPM transducer is right with the distributor.(see pics below) Curious thing is that when I connect a light bulb across the distributor I cannot seem to get the bulb to come on when the contact opens. The car sparks and runs fine. What am I missing. Do I have the wrong transducer. Any ideas?

[Early_S_Man]

Steve,

The Rpm Transducer/Speed Switch/Speed Relay isn't the problem ... that is the correct one for a carbed engine, and if it was shorted from a rusted transistor rattling around inside the case ... your ingition would have problems running!

Are you still using a stock Bosch CDI unit?

To get a test lamp to work ... try connecting it to +12 Volts and the distributor terminal, rather than across the distributor to ground.

[stevef]

Warren, yes I am running the stock CDI unit. However the PO was running a permatune unit with the speed switch. Would that make a difference. I put the CDI in because I knew it was a good unit and wanted to eliminate unknowns when I first started the motor after rebuild.

[Early_S_Man]

Steve,

No real difference of any significance between Bosch and Permatune as far as the RPM Trancducer is concerned.

The tach you have may be a unit intended for use with a ballast unit ... some/most of those tachs don't work with a point-triggered CDI system.

You may want to try building my bargain-bin tach calibrator that can also be used for such tasks as testing CDI units and RPM Tranducers ... as a pulse source ...