Jabsco Pump replaced but now running on

[richierich]

Hi all i recently had the whole Jabsco pump replaced on my SO 519 .. it was running erratically 

Now after replacement , it was running fine THEN it had low pressure and would just not stop running (have to turn off at panel)

under warranty they say no  ... not the pump but a leak in the hoses 

Does anyone know this problem, and which hoses should i look at  ie: the most likely culprit ? 

[jlasail]

Assuming that the water tank has water in it, check the filter at the ingress of the pump and make sure it is clean and not blocking the flow of water.
Second step would be to check if you have enough pressure in the air tank positioned right after the pump , you can use a bike air pump to slightly increase the pressure in the tank . It does not have to be very precise , just pump it up a little bit .
Then if that does not solve it, look at pipes and connectors after the pump (downstream) while the pump is running and look for a water leak, a small leak is enough to keep the pump running all the time.
Good luck.

[richierich]

much appreciated and makes sense but you would think a leak would end up in the bilge ? and there was no evidence of such,.. so ill take a look at the other suggestions first 

[ianf]

Two different things that have happened to me which cause the pump to overrun. the first was that there was a crack in the plastic cover of the filter housing which allowed air to be sucked into the system and the second was that I hadn't bled all of the air from all the pipes leading to all the taps (hot and cold) and to the shower heads.

Not sure what the arrangement is on your boat but on mine there is a relay which is triggered by the pressure vessel which switches off the pump when the system is up to pressure. Make sure that you wired it up correctly when you replaced the pump and that the relay is still good.

Good luck 

[rene460]

Hi Richierich,

In my experience, a leak on the discharge pump will only cause the pump to run continuously if it is large enough to require the full pump capacity.  In this case, it will very soon show itself in the bilge.  More often, a minor discharge leak will show itself as occasional blips of noise as the pump recharges the discharge system to the pump cutoff pressure.  The sort of thing you miss during the day, but will keep you awake at night.  

Of course if the pressure switch has failed or been adjusted in some way, the pump may not reach the set pressure, but that is another issue, and I don’t recall any posts reporting this as an issue.

The fault which will certainly cause the pump to run continuously is a leak in the pump inlet line from the tank.  This hose is at low pressure when the pump is running and can be below atmospheric pressure, especially if the tank level is low.  If the line is below atmospheric pressure, air leaks in, and the pump gets air in the pumping chamber.  It is a pump, not a compressor and cannot compress air to the switch set pressure, so the the pump runs continually.

Depending on the elevation of the pump relative to the tank, the line can be above atmospheric pressure when the tank is full, and the pump works as it should, but at some point the level becomes low enough that it is below atmospheric pressure, air leaks IN and the pump fills with air and then runs continually.

A common cause of inlet leakage is a crack in the cover of the inlet strainer, betrayed by an air bubble visible through the clear plastic cover.  You can try sealing the threads with a grease suitable for use in potable water systems, but if the cover is cracked you will probably have to replace it, unfortunately it seems to be only available as a complete filter unit, even though it seems a common problem.

If you can bleed the pump by opening a couple of taps fully when the the tank is full, and find that the pump then runs normally again until the level gets low, you have identified the problem.  On a recent thread, the issue started when the tank was about half full, but I don’t remember which boat model it was.

rene460

[Elcano]

Hi richierich,

when my pump was continuously running I had a blocked check valve, so no water flowed into the pump.

Good luck on your hunt.

Cheers

[Charlie-Bravo]

I would agree with rene, the symptoms describe a leakage of air on the suction side, a leakage on the pressure side will manifest as bilge water ……. or a continuously running tap, which I am sure you would have noticed, hose clips on the suction side can suck in air to a surprising rate without noticeable water leakage out.

CB