Model #3902508 CRAFTSMAN Well pump

  • Jet Pump Assembly
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Question and Answers


Why won't may Sears shallow well pump model 390.250253 pump up enough pressure to cut off?


Make sure that the pump is properly primed. A leak in the suction line could be causing this problem. Make sure that the foot valve is below water level but not clogged with mud or sand. A weak motor could also cause this problem. Check the owner's manual for your pump for other problems that could prevent the pump from working properly. We don't have the owner's manual for your model available online but here is the manual for a similar model: Owner's Manual Pump model 390.2508 .

If you are not able to determine the cause of this problem and resolve it, I recommend that you contact a pre-screened professional from the website to examine the pump and well to troubleshoot this issue.

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Lyle W -
Sears Technician
March 18, 2010

I have the same problem with my pump. It worked fine in previous years, but will now not build up pressure above 30 PSI. At 30 PSI I cam run all faucets together at full volume. When I turn them off, the pressure will not go above 30PSI. It will hold there after I shut the pump off and not loose prime when I turn it on again.

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clark -
September 16, 2010

Check the impeller and diffuser clearance where the impeller sits inside the diffuser. That union is lubricated by water, and wears over time, and if it develops enough of a gap, then water from the pressure side can enter the suction side, preventing the development of full pressure on the pump. In my case this was the problem preventing the pump from getting over 40psi.

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September 03, 2013

Ok I have to add my 2 cents I have had the same problem and have fixed this problem 6 times now for other people. First make sure there are no leaks in the suction side, if you use a bladder tank verify it holds pressure with water pressure at zero. Take pump apart. Note: the first time I did this I did not take out the Jet, venturi housing which was a mistake. Behind the Jet, venturi housing there is a gasket. Part 16 on sears parts direct. When I first looked at this gasket I noticed it was falling apart and missing in some areas Thinking this in no way could cause the problem but finding no other problems I simply made a new gasket out of a serial box approximately the same thickness as original. If you�re good with scissors this will not be a problem. After completing making new gasket and reassembling to my surprise problem was fixed. Apparently if there is a bad gasket or large cracks in the plate water will just do a loop in the housing and not build up enough pressure. This is a bad design to use a paper type gasket that is clearly a critical sealing surface I am trying to design a square cut oring to take its place. Hope this helps someone

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Craig -
September 09, 2013
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