Shurflo pump issue

[mol1jb]

Hey all,

I am having trouble with one of my shurflo pumps 4008 on 3/4in mainline. Here is what is happening:

There is a backup of sap in the mainline right before the pump. So first I tried replacing the screen filter, perhaps plugged - nothing, filter that was removed was very clean. Then I thought plug in the manifold before pump (T goes up to vac gauge then to screen filter). Took that off and inspected and looks good. Then I thought must be the pump. Here is where it gets odd. The pump is pulling 20" and maintaining good vac but little liquid is going through. Removed pump and took the diaphragm housing apart and everything looks good but I am no expert on the innards.

Any other ideas? I have another pump ordered to try replacing this one.

[BAP]

Do you have a recirculation line from your tank? If not, add one before the pump teeing into the line and use a needle valve to restrict the flow from the tank. Set the valve so you have a little steady flow out of the tank. That way your pump always has flow it, and you don’t get the dead heading that you get without the constant flow.

[Super Sapper]

If the trees stopped running you will get sap "stuck" in the line. You should be pulling better than 20" if the diaphragm is wet. Is the line sloped to the pump or level just before it?

[wmick]

I'm leaning in the same direction as SuperSapper. The fact that your gauge is showing 20" is the critical point, I think.... The pump is clearly working... and that sap should be moving... !! Unless no air or sap is entering the system above/behind it.... (like putting your hand over the vacuum cleaner hose) Could be you just have a very tight system right now with little or no sap flowing from the trees... Try pulling a connection apart, upstream from your sap, for a few seconds and see what happens... I suspect the pump will empty the line in short order.

[mol1jb]

If the trees stopped running you will get sap "stuck" in the line. You should be pulling better than 20" if the diaphragm is wet. Is the line sloped to the pump or level just before it?

Slopped. So your saying you get sap stuck in the mainline before the pump if your trees aren't running yet?

[Super Sapper]

Once you reach the max vacuum the pump will deliver it can't pump sap through until something comes in upstream.

[BAP]

OP, you have not my question as to wether or not you have a recirculation line? Having one is the key to making the Shurflo work the best because when you get up to 20” of vacuum and the pump runs out of liquid, it will maintain the vacuum but sometimes will not pump the new sap coming in because it gets kind of vapor locked. I went through this my first year and adding the recirculation line helped a lot.

[mol1jb]

OP, you have not my question as to wether or not you have a recirculation line? Having one is the key to making the Shurflo work the best because when you get up to 20” of vacuum and the pump runs out of liquid, it will maintain the vacuum but sometimes will not pump the new sap coming in because it gets kind of vapor locked. I went through this my first year and adding the recirculation line helped a lot.

Sorry, I do not have a recirc line on the shurflo. I did have one my first year on shurflo and then removed it and it didn't make a difference after I have over 100 taps per pump.

[mol1jb]

Once you reach the max vacuum the pump will deliver it can't pump sap through until something comes in upstream.

I guess that makes sense. This new mainline and laterals are new so I guess they are so tight that is what is happening. Thanks for the help.

[BAP]

I know mine will stop pulling the liquid at 19-20” range if it is not running hard enough or the re-circulation line is closed.

[mol1jb]

Well here in Central IL the last few days sap have flown like crazy. The shurflo is up to 25" with no recirc line on 70 taps. It looks like Super sapper was correct in his assessment as I am only having the sap stop up before the pump in the morning after a freeze and the trees are not awake yet. Thanks for the help.

[TreeTapper2]

Did you find any sap frozen in the line near the pump?

[whity]

I don't mean to hijack this thread. I'm kind of having the same issue. We have a shurflow pump setup, but it's only pulling 4". Sap is flowing from the closest dozen trees but hardly anything higher. Is there a possibility the main could be plugged up? Or bad diaphragm? It worked amazing last season pulling a constant 15 inches but can't get 5 this year. I have walked all the lines several times and can't find any leaks. Like I said the closest dozen trees are flowing nice. Just not the rest

[maple flats]

whity, do you have a re-circulation line, if not, start there. It is also possible if it has been like this all year that a check valve is stuck, in that case, remove the pump and run warm clean water thru it, then hook it back up again. If the diaphragm got damaged, change it. You want to keep a spare on hand at all times.

[whity]

Thanks Maple Flats. We do have a recirc line but have not used it. There is a steady stream coming out from the closest trees, so the diaphragm is wet. I'll try the warm water flush. I have a few replacement diaphragms I can change if need be.

[Bill Southern NH]

Whity,

Another thing to look for would be if you have a strainer. I have 4 of the shurflo pumps running throughout the season, and it seems that every year after putting the pumps back together, the rubber o-ring in the strainer gets moved and pinched. It doesn't happen very often, but it happens to me almost every season with one of them. When it does happen, it won't get much past 3" of vacuum. I hope this helps.

Bill

[SeanD]

Awesome thread. I'm having the same EXACT problem as the OP with one of my pumps. I have sap backed up at the pump, 20" of vac, and little to nothing coming through. Then all of a sudden there is a surge and it moves a ton of sap in a big 20-second pull. I can hear it gush in the tank. Then it will stop and I can see sap back up in the mainline again.

Ironically, I do have a recirculation line, but I disconnected it because the mainline always seemed to have liquid enough in the line and I could get 25-27" without it. I had just thought the recirculation line was to keep the diaphragm wet and increase vac. With all the sap backed up at the pump, it seems weird that the recirc line adding more sap to the system would help - though it does seem as if it is vapor locked like BAP said.

Strange also that my other pump doesn't seem to have this problem. It's remote, but whenever I spend time with it, it seems to have a constant flow. The one difference between the two systems is that the one with a vapor lock and sap backup has a manual bypass valve to go to gravity. Whenever I clean the filter, I close the valve to keep vacuum in the line while I'm disconnecting it. Then when it's all back together and tight, I open the valve. I wonder if I'm creating a pocket of negative pressure on the upstream side of the pump when I do that.

The remote unit with no problems has an automatic bypass that opens when I shut things down to clean the filter. I lose all vacuum, but I wonder if that's a happy accident. Any aerospace engineers out there?

When the next flow gets going, I'll play around with it. First I'll get all vacuum of the line and see what the pump does from scratch. Then maybe reconnect the recirculation line to see if that helps.

Thanks for all the advice here.

Sean

[West Sumner Sugar]

Regardless of flow, I leave my recirculation line cracked all the time. When I say cracked I mean it, just enough to say its open. It seems to regulate the flow, keeps the gauge from fluttering and seems to keep things moving at a constant rate.