Galley pump not switching off

[NickRobinson]

I have replaced a dead water pump on my, new to me, boat.
Off the boat, the new pump's pressure switch works perfectly, holding pressure (off) and running when on.
When installed, it runs continuously without cycling off. When isolated at the panel, the system holds pressure for days so not a leak.
Thoughts?

 

[KevinV]

What's changed? The installation.

 

[vyv_cox]

The pump's suction valve has debris in it. Presumably the discharge valve is holding, hence no pressure decay. Cleaning the valve will almost certainly solve the problem.

All pumps should be fitted with a suction strainer to alleviate such situations.

 

[NickRobinson]

Worth checking, certainly, but with a feed from a bucket and the outlet pinched shut, it performs fine.
There is an accumulator in the circuit, could this be a factor?

 

[NickRobinson]

What's changed? The installation.

Swapped out a dead pump for a working one of similar spec. All pipework untouched.

 

[billskip]

similar spec.

Mmm.... similar spec....similar....a slight difference can be the work or not result, it's imho to do with not achieving the pressure to switch off, when tested out of the boat how similar were the conditions?
½psi head difference could be the problem.
Is the pressure switch adjustable?

 

[billskip]

Worth checking, certainly, but with a feed from a bucket and the outlet pinched shut, it performs fine.
There is an accumulator in the circuit, could this be a factor?

If there are no leaks ,not even a drip the pressure should build up and operate the pressure switch...the accumulator really only prevents the pump switching on as soon as you open the tap so it minimise "hunting"

 

[wonkywinch]

Swapped out a dead pump for a working one of similar spec. All pipework untouched.

What killed the previous pump?

 

[NickRobinson]

Good point- it was DOA when I bought the boat,

 

[billskip]

Good point- it was DOA when I bought the boat,

Aha, so we don't really know the condition of the plumbing...mmm....
As asked earlier, is the pump pressure switch adjustable? Is there a lable with the operating pressures?

 

[ashtead]

Leaks in system -how clean are bilges now?

 

[Martin_J]

Is the battery supply voltage good? Perhaps not quite reaching pressure due to low power supplied.