BJ8 Tach Won't go past 2400 rpm

[Patrick67BJ8]

Just installed my Tach and it will not go past 2400 rpm when slowly reving the engine. This is part of the final leg of a 6 year frame-up restoration.

New wiring harness installed.
Negative ground.
Pertronix ignition.
Worked correctly before removing for full restoration.

Thanks,

 

[Patrick67BJ8]

Just installed my Tach and it will not go past 2400 rpm when slowly reving the engine. This is part of the final leg of a 6 year frame-up restoration.

New wiring harness installed.
Negative ground.
Pertronix ignition.
Worked correctly before removing for full restoration.

Thanks,

I should also have noted that the Tach falls off to zero after hitting the 2400 rpm mark and it will rev past 2400 if I goose the gas pedal while parked(it's still on jackstands).

 

[57_BN4]

I read a while back that the solution to this is to put a second loop of the white wire through the thingy on the back of the tach so it gets a better signal. Something to do with the Pertronix not giving as strong a signal to the tach as the points

Andy.

 

[rjc157]

I have the same prob with my bj8 it won't go past 2000 rpm I talked to nisonger they said it was the petronix look up their web they made a modern board that they configured with the petronix look it up

 

[Patrick67BJ8]

I have the same prob with my bj8 it won't go past 2000 rpm I talked to nisonger they said it was the petronix look up their web they made a modern board that they configured with the petronix look it up

Andy & rjc157, It's the same tach, tach wiring and the same pertronix. Something else...maybe? I did disconnect the "loop" to remove the Tach so I might craw up under the dash and see if the metal clip aound the plastic piece is inserted into the Tach far enough. I recall one of the metal legs is longer than the other.

 

[57_BN4]

The loop works as a transformer so is fairly sensitive to its orientation. Maybe try moving it around a little with the engine idling. Add a second loop if you haven't already, maybe you were just lucky previously. Lots of comments about Pertronix and no tach, many cured by the extra loop.