Never,
Mike is right. Pull a wire and make sure that you have a good spark at the plug. If so then I would remove all of the plugs and look at them and also turn the engine over if they are black or gummy to blow out any gas that is in the cylinders. If you have gas in any of them. it wouldn't hurt to squirt a small amount of
oil down in there so it can coat the walls as the gas will have washed them clean. I am running the high pressure Holly Blue Pump and have to have a regulator. I have a pressure gage mounted on the regulator just in front of the carb., and it only varies when I really get on it. The pressure will drop for a second or so as the opening of the carb. lets more fuel flow. but at a steady driving speed, the pressure should stay at whatever you have it set at. But be sure to check any fuel filters and make sure they aren't plugged. Also check you
oil for any signs of gas as a mechanical pump can let gas into the
oil if the diaphragm is starting to split.
Ron