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Topic: Pump cycle problem (Read 752 times) previous topic - next topic

Pump cycle problem

I 've been reading LOTS of past discussions re: short cycling. Read that I could test accumulator with a bike pump??
I wanted to trace the problem, myself, but when at MOT, paid Keith LOTS of money to have him take out the valve between new pump and tank, clean out some grit and replace original. He ran it for a while at the shop, but we still have the issue. I was hoping to shortcut the research.....sorry, but there was too much conversation about needing expansion tank or not, etc.
What can I do to not have the annoying short cycling and hammer noise?.
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Pump cycle problem

Reply #1 –
Disable the pump. Till repairs are made.
Scott

Re: Pump cycle problem

Reply #2 –
EASY to check the accumulator:

Shore water off
Water pump off
Open a faucet to bleed off pressure.

With a regular tire gauge, check accumulator pressure (remove the plastic cap in the center of the end to reveal valve).

If water comes out-- the diaphragm is bad and you will need to replace the accumulator.

If no water comes out, set pressure correctly-- correct PSI is 2 PSI less than pump cut-in PSI. OE pump, correct PSI is 23.  Yes, a bicycle pump can be used to pressurize it.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Pump cycle problem

Reply #3 –
And just how do you set the pressure??
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Pump cycle problem

Reply #4 –
The valve is just like the valve on a bicycle/car/motorhome tire.  So a bicycle pump works well.  Be careful using 100 PSI compressors/coach air, as the volume is SMALL and it would be easy to overinflate/blow it up.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Pump cycle problem

Reply #5 –
Thanks, Brett
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Pump cycle problem

Reply #6 –
Here is an Amazon page with accumulator tanks. The bigger the accumulator, the longer they will supply water without cycling the pump. If the pump does not pulsate much, then a small tank with do the trick. https://www.amazon.com/s?k=rv+pump+accumulator+tank&crid=1V0A19GLT6OHR&sprefix=rv+pump+accumulator%2Caps%2C208&ref=nb_sb_ss_i_2_19

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Pump cycle problem

Reply #7 –
When at MOT Keith took apart the valve between the pump and accumulator and washed out some grit. Can someone explain what the valve is What it does and how does turning the knob effect it
How many turns?
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Pump cycle problem

Reply #8 –
If your pump is recycling, you don't have an accumulator problem.....you have a leak. The accumulator does not hold pressure it merely supplies a steady flow of water by way of a bladder with less pump running. Even at 0 lbs the tank will still be full of water. First place I would look is the water tank fill valve. It is possiblel the water is running  back into the tank.
1994 U280, Build 4490
Deming, NM.

Re: Pump cycle problem

Reply #9 –
Let's make sure we are referring to the same problem:

Short cycling=water pressure pulsing when you open a faucet.  Bad or improper PSI on accumulator if OE style pump.

Pump cutting on/off with no water demand= leak.  Could be back to tank (leaky fill valve or bad pump check valve), could be external leak.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Pump cycle problem

Reply #10 –
Quote from: GleamB –
When at MOT Keith took apart the valve between the pump and accumulator and washed out some grit. Can someone explain what the valve is What it does and how does turning the knob effect it
How many turns?


That looks like the water fill valve.  Turning the knob you can manually close the valve.  If it is leaking through during normal sitting (switch off, but hooked up to city water), it will cause the fresh tank to fill even with the switch off.  In that case, you can shut it manually with that knob after you fill the tank, then you can use the water pump and run off the fresh tank. 
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Pump cycle problem

Reply #11 –
Quote from: Michelle –
That looks like the water fill valve.  Turning the knob you can manually close the valve.  If it is leaking through during normal sitting (switch off, but hooked up to city water), it will cause the fresh tank to fill even with the switch off.  In that case, you can shut it manually with that knob after you fill the tank, then you can use the water pump and run off the fresh tank. 
Yes. That will tell you if the valve is leaking or not. Turn off the pump and leave city water on all day and if the tank level goes up.....boom! Then you can close it manually and see if it does it again. As a sad aside, I found that my pump check valve failed. Took a while.
1994 U280, Build 4490
Deming, NM.

Re: Pump cycle problem

Reply #12 –
OK
The original problem was short cycling with no faucets open
 This valve that I posted a picture of goes from the pump to the tank BUT has something to do with the fill valve?
There is no apparent leak, but like Twig says, it could be something hidden. We don't use the fill switch. We direct fill.
Now for the real head scratcher......
Amy accidentally left a faucet open and drained the tank dry. After I refilled it, I waited to hear the pump short cycle, while the switch is on......Nothing!!! Been good for two days now.
It fixed itself.
BTW....Is what is being said here that I can turn the knob all the way to the right and it will .....what?? Shut water to the accumulator tank?. Still not clear, folks. I must be dense. What is the function of this valve....please.
If the accumulator doesn't hold pressure, then why did Brett have me check pressure of the tank. Confusing.
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT

Re: Pump cycle problem

Reply #13 –
Quote from: GleamB –
. What is the function of this valve....please.

Glenn,

That valve is your water fill valve.  When you activate one of the water fill switches the coil that is on that valve you show energizes thus opening the valve.  With that valve open water will go directly into the water storage tank IF you are hooked up to shore water and the pedestal spigot is turned on. If that valve is left open (one of your water fill switches is activated) it will cause the water to just recirculate through your system.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Pump cycle problem

Reply #14 –
Thanks Mike
So what happens if I turn it one way or another?
Oops. Just reread above
Glenn and Amy Beinfest
2001 36' U320
#5812
2014 Honda CRV

No Whining on the YACHT
 

Re: Pump cycle problem

Reply #15 –
Quote from: Pamela & Mike –
If that valve is left open (one of your water fill switches is activated) it will cause the water to just recirculate through your system.

Glenn,

Let me clarify this statement a little.
If you close off the shore water supply and this fill valve is left open, and you run the on board water pump to build pressure, the water will just recirculate in the system. This results in no pressure build up and the pump to run constantly. Lot of owners have made this mistake.

Now if this water fill valve has trash/grit under the seat it will let water seep backwards at a slow rate internally. If this happens then this will cause the on board water pump to cycle on as the system slowly looses pressure. With that valve being the new style ABS/plastic of some kind it is less likely to have calcium build up and cause the valve to leak through. If you do figure out that this valve is leaking through you can take out the 4 bolts that hold on the bonnet and clean the internal parts.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."