Last weekend I installed an inexpensive sunpro tach on a stock non computer controlled HEI. After installing it, I started my engine, the tach was working, and it ran for about 10 seconds. After this brief stint of excitement the engine quit running.

I diagnosed my engine not running and found it to first be a faulty coil, second to be a faulty ignition module and then ended up replacing the whole distributor.

The engine runs after replacing the distributor but I have two questions:
1) Has anyone ever seen a tach cause a complete ignition failure like this?
2) I'm paranoid now about hooking up the tach. I've got it wired and all I need to do is hook it up to the "tach" line on the HEI cap but am not sure if my ignition will fail again. Does anyone have an informed opinion as to whether or not I should risk reconnecting the tach? Right now my paranoia says I should not.

 

I've seen faulty tachs cause the engine to stall, but never had one that took components with them....just got another tach and went on down the road.

 

Coincidence.

The factory coil & module are known weak sisters. Just make sure you don't have anything hooked up wrong or shorted out on the tach and hook it back up.