Just because the convertor is new, doesn't automatically mean it's good. Double check the presure at the 1/8" pipe plug- should be 1.5 PSI. If it's good, sounds like a vacuum leak.Pushing the primer button makes it go full rich. Use carb cleaner to find the leak. Keep it running with your "little stick" and spray around the intake, throttle shaft and mixer gasket, if the RPM's pick up when you spray something- there's your leak. Dont give up on the C500! One of the best trucks ever made! Let me know how you make out- I'll try to help.
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