What he said, its usually a decrease in vacuum anyway from ICE to EV.The vacuum brake booster eventually leaks and needs to be replaced. It is unlikely to be caused by the vacuum pump. Leaving a car in a non operating state for a year or so while converting it can encourage the failure of rubber parts.
In my case, is this because the pump cycles on and off about every minute? Without appling the brakes, how often would the pump just come on with a good booster?sounds like you both need a new booster assembly
but are pretty hard to find.... or replace master cyl with an appropriate unit not needing vacuum. Probably NOT a good idea with a lead build trying to stop the extra weight without a little help.Manual brakes provide a suitable interval.
Are check valves always needed?the pump should NOT cycle at all, for many days, unless you use the brakes. You either have a leak, and bad check valve, or the check valve installed in the wrong spot allowing vacuum to escape back thru the pump itself.
It is highly unlikely that any of these little pumps pull more vacuum than the ICE manifold, so are unlikely to damage anything. In fact, at altitude the pump is de-rated significantly, so you have to set the vacuum switch considerably lower, or the pump never 'finishes'.
my pump is supposed to pull 23" at sea level, but at 7000' I had to set it down to about 13" so that it would 'finish' relatively rapidly.