I have a Jabsco fresh water demand pump. Recently, after several years of use, it has been short cycling, running for less than a second very frequently. So far I have not found any leaks in the system, that still might be the problem but I am wondering if it is actually a pump issue.
water pump short cycling
- Thread starter gettinthere
- Start date
Most likely the pump has an internal leak. To test this, disconnect the output hose and plug the line coming from the pump. If the pump still cycles, the issue is internal. If it's possible to open it up and clean the check valve, that may do it.
Ken
Ken
If it pulls air in on the suction side the pressure will drop on the output side, resulting in the pump cycling. Check in the filter for air bubbles.
I think there are two reasons for short cycling. You have probably already checked for leaks at fittings and faucets. But sometimes the internal check valve in the pump itself goes south. And leaks water back to the tank. Dammed hard to troubleshoot. Not sure about the Jabsco but some pumps can be tore down and all the moving parts wiped with a paper towel and re-assembled. Temporary fix at best.
The cycling happens because the pressure in the pump drops, the pump increases the pressure, the pressure drops, repeat ad nauseam.
It could be a slow drip in a faucet. Could be a slightly loose hose connection. If you have an accumulator tank, the tank could be losing pressure.
This year I replaced the pump and accumulator tank with a Shuflo demand pump. I'm very happy with it. It works and it is quieter than the previous pump.
It could be a slow drip in a faucet. Could be a slightly loose hose connection. If you have an accumulator tank, the tank could be losing pressure.
This year I replaced the pump and accumulator tank with a Shuflo demand pump. I'm very happy with it. It works and it is quieter than the previous pump.
Our older Flojet freshwater pump was doing the same thing. It would burp every ten seconds or so. Turned out to be a leaking check valve. I decided to install a new Flojet, but also replaced the check valve in the old pump. Now I have a spare.
When we purchased our 1991 boat in 2002 the PO had the problem at that time, but must have thought it was the pressure switch. I did eventually find a drip leak in a very hard to get at place on the boat that was causing the pump to burp every so often. Fixed the leak and the burp stopped for awhile. Then it started again, but no leaks in the system. After giving the symptoms to the manufacturer technician, he said it was likely the check valve, and it was.
All of these pump manuals have very good troubleshooting sections. We've almost all had these issues, at least those of us who have had their boats for quite some time, as well as newcomers. Big tent! 
Knock on wood our 30 year old pump is still working well. I have a new backup pump on board. I repaired a pipe leak by replacing all the hoses a few years ago. Good luck.
Knock on wood our 30 year old pump is still working well. I have a new backup pump on board. I repaired a pipe leak by replacing all the hoses a few years ago. Good luck.took the pump apart, could not find anything obvious. Reinstalled and it still cycles. So I replaced it with the spare pump on hand and no more short cycling. So it is the pump and not a leak.
Thanks to all.
Thanks to all.