Jet pump rapid short cycling at cut-out
My jet pump (1/2hp) has started cycling very rapidly at the cut-out (40psi). Cycles perhaps 4 or 5 times in the space of a few seconds...pressure guage fluctuates rapidly with it and then shuts off and sits happily at 40psi. It will do this every minute or so without any demand in the system. Lights in the cottage flicker wildly and the pump gets, of course, quite hot until it shuts itself completely down, cools off and starts doing it again.
New 25 gal pressure tank last summer. 18psi charge in it.
Cut in on the motor is 20.
New pump last summer.
No leaks anywhere.
Foot valve is ok.
There is no check valve on the system.
We're pulling water from the lake (cottage system).
I started the system up this past Thursday (today is Sunday) with no issue (had everything running in 10 minutes flat). I winterised the pump properly....poured plumbing antifreeze directly into it as I do every fall. Rest of the system I blow out. Anyway, it started cycling on Saturday. Normal cycles have been the 2 to 3 min range...normal in my opinion.
Wondering one of two things....
1) the pump is about 135 ft away from the panel....running 14/2 wire. Am I getting too much resistance? But if this was the case why would it cycle like this only at the cut-out. I have noticed that this pump does dim the lights very briefly when it cuts in where the old pump didn't (we burnt out the old pump because the tank failed....don't ask!)
2) at every start up in the spring it does take a day or two to have the water come "clean" and not be spitting up dirt etc. after I drop the foot valve back in the lake. Has there been some grit hurt the impeller or better yet, the pressure switch.
Any ideas out there before we go back up this weekend? I really don't want to be buying a new pump!