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Topic: Fresh Water Pump loses prime (Read 556 times) previous topic - next topic

Fresh Water Pump loses prime

Hi All,

Shurflo 4048 Fresh Water Pump loses prime at 1/4 tank.  Strainer is clean.  No apparent leaks.

Ideas?

Thanks

Don
Don & Sue
2009 NImbus 38
2020 Jeep Grand Cherokee toad

Re: Fresh Water Pump loses prime

Reply #1 –
Is that 1/4 tank from a visual check at the tank or through the monitor?

Mike
Pamela & Mike 97 U 320

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

Re: Fresh Water Pump loses prime

Reply #2 –
Quote from: Pamela & Mike –
Is that 1/4 tank from a visual check at the tank or through the monitor?

Mike

Yup, when you look in the pump's pre-filter, do you see water or air when this happens?
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: Fresh Water Pump loses prime

Reply #3 –
1/4 tank is visual on the tank.
No air in the strainer.

Don
Don & Sue
2009 NImbus 38
2020 Jeep Grand Cherokee toad

Re: Fresh Water Pump loses prime

Reply #4 –
That is strange.  With no air in the suction strainer and water in the tank then this is more like the pump just quits delivering water. Like I said this is strange if you lose prime you should have found air somewhere in the pump suction side. Now it could be something left in the tank during production that gets sucked into the suction piping once the tank gets low causing a restriction. The thing is if it was a loose piece of construction material seems like it would get sucked up at various tank levels rather than just at 1/4.  If it was a bad check valve in the pump you would see pressure/volume problems no matter the tank level. More brain time is required till I come up with something else.

Mike
Pamela & Mike 97 U 320

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

Re: Fresh Water Pump loses prime

Reply #5 –
Fill solenoid off?

Re: Fresh Water Pump loses prime

Reply #6 –
My fresh water tank has a small cone shape sediment filter 1/2"x 2"  that slips into the 1/2" female outlet spin weld fitting. You would have to undo supply line connection to pump at the tank and use a curved pick to pull it out if you have one.
Doug W.
96 36' U270 CSGI #4946
04 Toyota Tacoma 4x4
PNW

Re: Fresh Water Pump loses prime

Reply #7 –
On my coach the pump is at the bottom of the tank so the water gravity feeds to the
pump so if your system is the same I would think there is a blockage some where.
Blow the line back into the tank to see if it is opened.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Fresh Water Pump loses prime

Reply #8 –
Fill the tank to half full. Check the flow at the kitchen.  If the flow is adequate check the plumbing from tank to pump. If no issues are found, make sure the pump is not pumping back to the tank, then think pump.
Tim Dianics
Pam Sapienza
Vader PupZilla Labrador Canine Beast (AKA Pup)
Columbia, MO
1996 U320 4000
2021 Jeep Gladiator, Diesel

Re: Fresh Water Pump loses prime

Reply #9 –
I think I figured it out.  Prior to my last trip the water fill valve failed, and I replaced it.  During the trip the pump would come on every minute and cycle for 2-3 seconds, so we turned the pump off when not in use.  Pump would lose prime at 1/4 tank.

When I got home, replaced the defective water fill valve.  Pump no longer cycles.  Just drained tank down to below 1/4 tank and the pump seems to work OK.  Next trip scheduled for later this month will tell.

So, it seems like the defective water fill valve was the culprit.

Make Sense?

Don
Don & Sue
2009 NImbus 38
2020 Jeep Grand Cherokee toad

Re: Fresh Water Pump loses prime

Reply #10 –
Quote from: djpauls –
So, it seems like the defective water fill valve was the culprit.
Make Sense?
Sounds reasonable.  On the older coaches (like ours) that have a manual fill valve, if the fill valve is left open and the water pump is turned on, the pump will run continuously but the water system will not have any pressure.  The water just goes in a closed loop from tank to pump and back into tank.  Has caught many new owners by surprise when they experience mysterious loss of water pressure.  A gentle suggestion from Forum members to "Try closing the fill valve" often solves the problem.  Perhaps you had a similar condition that was cured by replacing the fill valve?

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"