Freshwater pump (house water) cycles on and off?

This morning the freshwater pump supplying the plumbing systems on the boat started cycling on and off (about 2 seconds on and then 2 seconds off when a high flow faucet is opened).* It is the Jabsco Model 31765-0092 two stage pump that has worked fine up until this episode.* It still provides water but at low and variable pressure.*
It almost seems like it can't figure out that there is a sustained demand?*
The troubleshooting guide doesn't cover this issue.* I cleaned the strainers (the one in the upper housing had some gunk in it) and there are no obvious changes to the system piping that would account for this.* When reading the manual, I discovered that when I'm away from the boat for extended periods I'm supposed to turn off the water pressure circuit (which I do) and open a faucet to bleed system pressure (oops).* Might this have caused the problem?
Before I start randomly tearing things apart, I would sure like some suggestions on where to start and thoughts on what might be causing this.
Thanks!
Jim
M/V Antipodes

Mine was doing it last week, but it turned out to just be a dripping faucet in the head. Maybe look for a small drip in the systems post-pump?

This only happens when I open a faucet.* If there was a leak then the pump would just periodically cycle on and off continually.* Just to be sure, I went and checked all of the post pump systems and there are no leaks I can find.

I would start with a new pump and keep the old as a spare.* We have to replace our pump about ever couple of yeas being a live aboard we use the pump a lot. I fill the water tanks rather than connect to the dock domestic water.* In fact this morning a nieghbor woke up with 2 ft of water in the bilge.* The cause was a water domestic fitting.**Over the 11+ years we have been a live aboard I have seen to many boats damged/one sink becuase of the domestic water line breaking.

If its was just cycling on and off then it would be a leak/drip.* Ours cycles on about 1 to 2 seconds ever 6 to 8 hours.

Do you have an accumulator tank? If so, sounds like it's failed. My first boat acted like yours all the time, because it didn't have an accumulator tank.

No accumulator tank.* The two stage water pump is intended to eliminate the need for the accumulator tank and it has worked fine up until this morning.

Sounds like maybe the pressure switch has failed.* I agree, new pump, saving the old poorly working one seems to be something only those of us from Maine would do.

Well, here in the south we would by-pass the pressure switch with a momentary switch bolted to the side of the sink. Stainless steel can be hard to drill when mounting the switch- so you may want to just screw the bracket onto the cabinet door below the sink. Just turn on the faucet, then push the button until you have enough water for your needs.Showering, of course, will take a little more effort. You may want to enlist the help of a trusted family member. You in the shower, they at the kitchen sink to hold the button.


If all this sounds a bit cumbersome, maybe you should just follow the suggestions in the previous posts.
Steve

This is a fancy pump that uses an electronically controlled permanent magnet motor in order to run at any speed necessary to maintain water pressure without cutting in and out or needing an accumulator.* So there's no switch to bypass ... the motor won't run at all without the electronic control.

One thing to check is the power feed to the motor.* They note that "The Dual Sensor Max VSD should be wired to the powersupply through a switch rated for 25 amps", so the first thing that I would do would be to measure the voltage *** at the pump *** when it's running.* I'm wondering if a corroded connection, bad breaker, etc is lowering the voltage when the pump load goes up, which causes the electronic control to reset, turning the motor off, which then lets the voltage rise again so the pump starts again.* Measure between the power feed and the pump ground.

Otherwise, I'd say it's probably the controller... which may or may not be less expensive to get than replacing the whole bloody pump.*

Well I replaced the pump and it's working perfectly (and the Admiral is once again happy).* I also got the rebuild kit for the pump and will add "Rebuild freshwater pumps for storage as spare" to the never-ending list of boat projects.* Thanks for all the replies!
Jim
M/V Antipodes

P.S.** Departure in 17 days for our trip around the world!

Around the world?
Steve

Yep.* After 2 years of preparation (and learning how to actually handle this boat), all of the pre-departure boat projects are complete (except for taking on 3000 gallons of diesel) and we'll be getting underway on October 31st.* We'll have a website up and running in a week or so and I'll post that address here for anyone that wants to follow us.
Jim
M/V Antipodes

Even in the USA it is possible to purchase fuel "in bond" .

3000G is enough to get a truck delivery.

That means an offshore boat will not burn the fuel while in US waters, you sign a piece of paper.

Might save enough to hoist a Marguretta for me at your first stop.

Bon Voyage

FF

I'm actually getting a truck delivery in Mexico at the commercial price (cheaper than anything I've managed to find in the US).* Don't worry though....I'll still hoist a margarita to you anyway!

Jim

Jim:*

I'm really looking forward to your travels as I think this is one of the major categories the founders had in mind when this site was founded.

We're going to be posting the journal of our trip on our website at www.yorksafloat.com.* The website is up but still very much under construction.*

Jim
M/V Antipodes