Jabsco head question

[YukonRon]

Our 2013 R-25SC has a Jabsco manual pump head, which has not worked properly since we bought it last fall. During the sea trial, we found that it would not pump water into the bowl; but if we filled it manually it would pump out. The dealer chose to send me a complete pump assembly to fix the problem.
I have now replaced the complete pump assembly, with joker valve, etc, but I'm not sure if it is working properly. When I pump water into the bowl, it also pumps out at the same time, so that only a small amount of water remains in the bottom. If I fill the bowl manually, it will stay in the bowl and I can pump it out as normal.
Since this unit has never worked properly, I'm wondering if this is normal operation? I would have expected that the wet setting would pump water into the bowl and it would stay there, allowing you to leave the bowl partly full, like our toilet at home, so stuff doesn't stick to the bowl.
Did I do something wrong, or is this working as it should? Suggestions?

 

[Osprey]

The Jabsco manual head pump does not have a "fill only" setting. There are only two mode settings: wet bowl and dry bowl. Further, the pump is dual acting. First consider the mode lever set to wet bowl and the pump handle in the down position. As you pull the pump handle up the following happens:
1. first cycle air, thereafter water in the pump barrel above the piston is forced into the bowl
2. material in the bowl, such as water and waste, is drawn from the bowl in the barrel below the piston.
Now pushing the handle down:
3. draws water into the barrel above the piston
4. forces material below the piston (which was initially in the bowl - see step 2) out past the jocker valve.
The action with the mode lever in the dry position. Pulling the handle up:
5. for the first cycle water may be in the barrel above the piston but on all subsequent cycles only air will be above the piston. Whichever is above the piston goes into the bowl
6. material in the bowl is drawn into the barrel below the piston
Now on the down stoke;
7. air is drawn in above the piston
8. material below the piston (step 6) is forced past the jocker valve.
After several up and down cycles on the dry bowl setting the bowl is empty and only air is in the barrel above the piston.

 

[DBBRanger]

If I may, I have a question that may or may not apply to the OP's question:

The action with the mode lever in the dry position:

Osprey,

After rebuilding the head, I find that I must physically hold the lever down in the dry position with one hand while pumping with the other. Before, I didn't need to hold it down. Do you know what I might have done wrong - I assume one shouldn't need to hold the lever down while pumping.

 

[YukonRon]

The Jabsco manual head pump does not have a "fill only" setting. There are only two mode settings: wet bowl and dry bowl. Further, the pump is dual acting...

Osprey, your explanation makes perfect sense to me. I do not see any opening or port in the piston barrel that could be opened in the wet position to prevent it sucking the water from the bowl on the upstroke.
However, I found this statement which I had previously overlooked in the user's manual:

"Before use, ensure that there is enough water in the bowl to prevent the toilet paper becoming compacted at the bottom of the bowl...If the bowl is empty, move the Flush Control Lever to the Open position and pump the handle up and down until the flushing pump is primed and water enters the bowl"

So, is this suggesting there should be standing water in the bowl? Is it just pumping some water through so the bowl is wet? Or is this just another case of some leftover wording inadvertently transferred to the instructions during the cut-and-paste process while taking documentation from another model?
Still not 100% sure.
I will do some more experimenting and go through their warm water priming procedure today and see if that changes anything.

 

[YukonRon]

If I may, I have a question that may or may not apply to the OP's question:

The action with the mode lever in the dry position:

Osprey,

After rebuilding the head, I find that I must physically hold the lever down in the dry position with one hand while pumping with the other. Before, I didn't need to hold it down. Do you know what I might have done wrong - I assume one shouldn't need to hold the lever down while pumping.

DBBRanger, on my head, both the old and new units, the mode lever clicks into position and stays in place. There is a plastic cam inside (see item #20 in the attached photo) which should lock it in place as it holds the valve . There is also a spring inside (item #35), but i believe it is just to hold the valve flap in position. (I haven't had this section apart yet). My manual says "Valve Spring (Only from 1998)".
Hope this helps.

 

[DBBRanger]

the mode lever clicks into position and stays in place. There is a plastic cam inside (see item #20 in the attached photo) which should lock it in place as it holds the valve

Ron,

Thanks - looks like I have a project!

Doug