You need 12 volts to it, or the bi-metallic arm will not bend and you will be stuck with low control pressure = rich mixture until the engine is fully warm. Once the engine is warm, the engine heat will cause the bi-metallic arm to bend.

But the WUR is powered by the fuel pump relay, pin 87, not the ignition circuit, so you need to jumper the relay to test. If your car has the safety switch on top of the fuel distributor, you can pull that off to get power to the WUR.

The lump on the plate was probably the grease used to hold the pin in place during assembly.

But something else may be going on with the fuel economy. A first step would be to check control pressure and get a CO reading.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe