MSD CD Problem

[lordy]

Mechanic installed a new MSD CD on my 77' 930. He also sent the tach to a shop to have it upgraded to the new system. The car runs fine, but the tach is now erratic. Sometimes the tach works, but sometimes not at all after the engine is started. When it does work, the idle indications are way too low and when engine is rev'd, the indications are jumpy, slow, stuck for a sec... He has checked the wires and the hookups at both side and believes they are correct.
Any thoughts on this problem?

[john walker's workshop]

there's a tach stabilizer i used in the past. from MSD. looks like a 2"x2" transformer. what was wrong with the original one? they put out a very nice spark.

[lordy]

Thanks John for the reply.
The original CD was diagnosed as bad after having sporatic engine running problems. Due to a very high OE CD replacement cost, the MSD was used instead. The original tach was sent to California to be modified for the MSD. I'll look into the MSD stabilizer, but I wonder if it will resolve the tach working at engine start and being erratic or not at all (pegged at zero).

[RoninLB]

Originally Posted by lordy

MSD. I'll look into the MSD stabilizer, but I wonder if it will resolve the tach working at engine start and being erratic or not at all (pegged at zero).

it's worth a try and easy to hook up. It's probably around $75.

I use one.

[ischmitz]

Bosch CD units can be rebuilt. I would have chosen that route and keep the car original. Our host actually sells the rebuild service. See here: http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_ELignt_pg6.htm#item23 or do a search for part # A-602-702-00R

Cheers,
Ingo