Sump Pump cycles 3-8 times each time it runs
I have a couple of Zoeller M53 pumps in separate sumps at each end of my basement. One has always worked fine, but the other has a consistent issue: every time it runs, it first pumps the water out of the sump, but then cycles on/off anywhere from 3 to 8 times before finally stopping. Each of these on/off cycles is very short, on the order of 1-5 seconds.
From what I've read in this forum and elsewhere, this would indicate a problem with either the check valve or the float switch, but I don't know how to isolate it to one or the other.
When this happens, I hear and feel a "clunk" each time it cycles, but I don't know whether this is coming from the valve or the pump because they are close enough to each other that the vibration is carried up the pipe, and it's hard to localize based on hearing. I also don't know whether the clunk is a symptom or cause of this problem.
At any rate, I have to think that this extra on/off cycling can't be good for the motor, and beyond that it is driving me nuts. Any advice for the best way to approach this?