Where to start?

[PMF1984]

My washdown pump is not working.

With the breaker on, I have good voltage to the pump.

On a whim, I checked the voltage with the breaker off: - 0.4v

I checked the voltage at the breaker post; turned off: 0.0-0.1 v

Starting to chase the wires... anything else I should be looking for?

 

[High Wire]

Does it have a pressure switch? Can you remove the discharge hose at the pump? Maybe it’s pressurized.

 

[twistedtree]

I’m not understanding, I think. You have good voltage at the pump with the breaker on, and essentially zero voltage with the breaker off. That’s what’s expected. So I’m not sure why you are tracing wires?

From what you have described, it sounds like an issue with the pressure switch in the pump, or the pump motor.

 

[C lectric]

The near no voltage with the switch off and breaker off is what should happen.

Instead check the voltages at the pump and on the ground wire. Maybe you have a faulty ground.

Have you checked the working voltage at the pump when you turn the pump on and it actually tries to run or at least is set up to run. You may find that the voltage drops precipitously meaning there is at least one poor connection in either or both of the + & - leads.

Do not ignore the breakers/fuses looking for poor connections. I have seen
breakers fail and fuses and their holders develop resistance causing a large Vdrop when a load tries to operate.

Try an independent Vsource to the pump to check it actually runs or you will waste a lot of time checking all the other potential problem sources. The jumper wire does not have to be pretty as it is just a test of the actual pump.
I would though fuse it properly.

As suggested is there a pressure switch as part of the pump? Likely there is to protect the pump when you stop the water flow. They can be common sources off pump operation failure.

 

[mvweebles]

When was the last time you used the washdown pump and how old is it? Typically raw-water, these have a high failure rate due to long stretches of disuse. You can try whacking the housing and/or pressure switch with the handle of a screwdriver to see if something loosens-up.

Peter

 

[MYTraveler]

If it wasn't a lot closer to zero, I would want to know why. It suggests to me that current is getting in on the ground side, which probably means that you have one or more bad ground connections to the battery.

 

[PMF1984]

Ok, so a little update.

I traced the wire back to the Control Panel. Two things. One, the wire is 14 ga. and 12 ga. is called for. Two, the wire went back to the breaker for the “Below deck lights”

Still,unresolved, what wire is on the wash down pump breaker, and what about that 0.4v.

Will report letter today.

 

[PMF1984]

Fixed

Thanks for advice.

To recap:

The pump made a hum but did not pump water.

I hooked up a hose to the discharge side to make sure the hose leaving the pump and the valve in the bow were not clogged. That worked out.

I removed the line between the filter to the pump to make sure it as clear while I also cleaned the filter.

I had a diver scratch at the intake for the pump while I got my 3 month bottom wipe.

That left the thru hull shut off, the line from the thru-hull to the filter and the pump.

Which brings us to today.

(I had ordered a new pump so I had it on hand, just in case.)

1. The voltage on the ground side was solved by tightening up the ground wires on the control panel that connect the 4 ground bars.

2. The "problem" with the pump (not sure there was one) was solved by installing a new pump.

3. The 14awg wires to the pump were replaced with 12 awg.

Put power to the pump.....no water.

4. I cut the out hose out between the thru-hull shut off and the filter.

5. Turned the shut off valve on the thru-hull and got wet immediately. At least now I knew I would not need a haul-out to replace the thru-hull.

6. When I removed the hose I saw a little something poking out of the filter end -- palmetto bug?

No, not a palmetto bug. It was a little glob of grease that was in the thru-hull shut-off valve that got mixed with "stuff."

7. Put on new hose - water

 

[diver dave]

Thanks for advice.



To recap:



The pump made a hum but did not pump water.



…

I would suppose that a DC motor that hums, is actually running.

 

[High Wire]

Well now you have a spare pump.

 

[mvweebles]

Sounds like you have a separate thru-hull for raw water. Depending on size of your sea strainer relative to your engine, might consider a manifold off your sea strainer so you pull water through it vs a small strainer.

https://www.groco.net/products/fittings/manifolds/raw-water-manifold

Note the fine print - Groco more or less disavows this as a good idea due to contention with engine. An inline check valve solves much of the concern.

https://www.groco.net/pnc-1000

I like over-sized sea strainers with manifolds vs multiple thru-hulls scattered throughout the boat. My Perkins 4.236 75hp has a 3/4" inlet and Installed a 2-inch thru-hull with sea strainer and the washdown pump off it. But you really have to do the math - a 2-inch hose has a cross section of 3.14" and the 3/4" inlet hose for the engine has 0.44" of area, so less than 1/6th the capacity. A Seachest is better, but not in the cards as a retrofit for most boats.

Peter

 

[PMF1984]

Diver Dave,

Yes it hummed (which meant the pump was working) but on the other hand no water.

So I checked the various parts of the system in the order of difficulty. It was easier to replace the pump than it was to get that first section of hose changed out. Some things are more accessible than others.


Highwire, yes it's always nice to have a spare. I remember when my fresh water pump went out.

MvWeebles,

It wasn't the intake, it was the 90 degree elbow just before the filter that got clogged. but thaqnks for the suggestion.

 

[ronobrien]

My washdown pump is not working.

With the breaker on, I have good voltage to the pump.

On a whim, I checked the voltage with the breaker off: - 0.4v

I checked the voltage at the breaker post; turned off: 0.0-0.1 v


Check the ground side also. You may have good power but a bad ground.