Save your self some time, you don't have to remove the carb or the heater to test it, if it's bad then remove the carb, just hook 12 volts to the choke heater and see if it opens give it a five + minutes, did you check the plug with the van running for 12 volts, make sure that the carb mounting bolts haven't loosened up and the carburetor has lost it's ground, is there any corrosion on the carb. Good luck