if the tach is dropping to zero quickly then it is ignition related.
check things like 12+ volts AT the ign box or dizzy or coil.
if it was fuel it would cut out, but the tacho would not sharply drop.
does it do it under load ? when driving ? or in nuetral as well ?
check the float levels.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.