close friend of mine gave me a jet pump that would be useful to run some extra sprinklers, I have a well so do not use city water...

my problem is the pump does not seem to want to accept that I have 'primed' it correctly or there is something that I am not catching. I have made it pump several times after 'priming' it but other times no success.  I prime it and it seems to be OK cause the pressure is good, then I 'crack open' a spigot and the pressure disappears... the times that I have achieved success is when I open the spigot super slow and watch the pressure to try and not to let the pressure go down.  The options I can think of are the impeller is not good (this pump is 40+ years old) or air is getting in somewhere to break the suction on the pump....   ?any other ideas?    I am not a plumber by any standard...I do not know what kind of impeller these jet pumps use.    Peace, Floyd

It is a Flint & Walling pump. 1/2 horse motor

If you are using a "foot valve" only in the well DiyDave is very correct as many are not a perfect seal always. I've also seen them "foul" with sediment, sludge, or algae in the well not allowing their closure and seal. Also, a minute pinhole, or even a loose clamp will allow this suction line to drain back into the well over a few minutes, to days unless used repeatedly.

An easy option is to install a check valve into the line that is positive sealing just after the foot valve. Also, if using flexible plastic pipe on the suction line double clamp your connections using two stainless worm clamps at each connection. Myself, I always warm the connections with a propane torch before pushing and clamping the connections together. That way the clamps force the joint to conform to the connection. 

simple test...

prime the pump/pipe but do NOT screw in the tiller plug. Water should be 'on the lip...full.

go have lunch, take a walk, turn wrenches, have a nap.....

come back 1-2 hours later

IF water is NOT 'on the lip', it's leaked out 'somewhere'....

query, how deep is the well, how long are the pipes and how HOW are the pipes ?

What model of Flint and Walling pump?  What well depth (for lift), and are you running a two-pipe riser, or a single? 

Frequently this kind of problem is either a configuration issue, or erosion of the nozzle coming into the pump's volute.  The volute nozzle on many jet pumps is frequently made of bakelite or similar hard plastic, and as the pump ages, incoming sand wears at it.  When the pump sits for a while, rust flakes on the inside of the housing gather, and when started up without cleaning first, those flakes get wadded up and smashed against the nozzle, making the jet pump pretty darned ineffective.  The third issue, is that one or more of the impellers is either no longer tight to the shaft, or eroded/broken away such that it's not spinning water.

The reason WHY a Jet Pump works is simple-  Centrifugal force.  There's water inside the volute, and the pump impeller stack is spinning it around in a circle fast enough to make it want to be against the outside of the housing.  When centrifugal devices fail to work, it's usually a very simple problem.

If you haven't opened it up for a look, that'd be the best step.  Flint and Walling's webpage looks pretty good, they probably have downloadable service documents on that pump.  If you pull it apart and find a damaged nozzle or spun-out impeller stack, they probably still have them available...

Thanks guys... It is straight from the well into the pump, on to the garden hose(s)... Since it is an older pump I am going to try Jay's idea of "leak back" and also consider what Dave said about being a older pump and something is awry... may look deeper into this OR spring for a new pump . and let Social Security pay for it, or my work subbing for other priests when they want a day off or have to be someplace on the weekend.

Enjoy the heat of summer, cool is a couple months away.   Peace, Floyd

Again thank you and an update

I got'er going... I kinda knew that the foot valve was good cause i could 'pump' water by raising the down tube and pushing it back down quickly SO I accidentaly noticed that the connection of the pump to the down tube was not tight. That got some permatex to make sure now air leaks there.  In the meantime i also did some looking on this wonderful web to learn more about jet pumps ... mine is a shallow pump cause the jet is bolted on to the pump and not down in the well... by the way my water level is less than 20 feet give or take.

last night I gotter going and after a long pump shut off the outgoing valves and let is rest for 15 min and it started again.. ... ... ... then this morning i saw that it was still holding at just above 10 lbs. of pressure so I turned in on and opened a spigot without any hose and it started slowly then started the air and water routine but got going with the water only and I think we have success, yea.    Again Thanks guys, this old pump still has some muscle.  Peace Floyd