[Double Venom]

Andy,
Grounds are CRITICAL on these cars. Yes #190 black wire going to the sending unit is mandatory BUT do your self a major favor-leave the 190 hooked up BUT add a short ground wire from one of the pick up bolts, directly to the frame! Ever since our third Cobra we have added the extra ground-saves all kinds of possible future problems!

Now check that the Gauge also has a proper ground.
CR's uses a stock OEM GM sending unit- '0' to 90 OHMS.
It IS very possible that the Gauge OHMS and the sending unit OHMS do NOT match!

Mickmates sending unit IS an excellent unit, PEGASUS also sells this type, but again The OHMS have to match, or your gauge will do what yours is doing! Difficult to install on a completed car but it can be done.

Make sure the "arm" in the tank is totally free to swing! I have seen some put in where the "Float" actually hits the pick up arm/tube or the edge of the tank in its full swing motion.

Irritating, but an easy Gremlin to kill!
DV