When the Taco Valve is open the circulator pump will not come on. It appears there is no juice to the relay when it calls for heat. The pump comes on if I go through the thermostat and disconnect the zone valve completely. It's a brand new zone valve head.

This is a gas hot water baseboard system, using Taco zone valves, taco transformer, and circulator. Thermostat works, new zone valve head, circulator and relay work if I hook it directly to the Thermostat and bypass the zone valve. 24V between 1 and two when thermostat turned up. Goes to 28V when it opens and voltage between 1 and 3 is now 28V.

Check the wires between the zone valve & relay. You could have a broken wire.

The thermostat needs to activate the pump and the zone valve with parallel circuitry, not series. Did you wire this yourself?