Jabsco not priming

[Kevin davis]

Hi all.i have jabsco raw water pump that won't prime.i have checked hoses and clips right through to pump and found no issues.ihave water making it's own way to pump inlet.i can get it to work perfectly if I disconnect outlet pipe and suck it then reconnect to heat exchanger problem comes when I turn engine off.when I start her up again I have to repeat sucking process.i have found a very slight drip at back of pump but not enough to cause system to drain in such a short space of time.any help appreciated thanks guys

 

[fisherman]

Wear can do this. usually the faceplate, backplate inside the pump even if the impeller is good. The drip suggests backplate.

 

[Kevin davis]

ok thanks for your speedy reply.i have a spare pump but driveshaft to short.il take plate off that 1and try that today as they are the same pump.with different length driveshaft.i will let you know how I get on.thanks again

 

[fisherman]

ok thanks for your speedy reply.i have a spare pump but driveshaft to short.il take plate off that 1and try that today as they are the same pump.with different length driveshaft.i will let you know how I get on.thanks again

the pump depends on the seal between impeller and back and face plates. The back plate is often forgotten.

 

[Kevin davis]

I will check both today and let you know how it goes.cheers

 

[fisherman]

I can't remember exactly but there are seals and bearings to consider as well. All obtainable.

 

[Plum]

Hi all.i have jabsco raw water pump that won't prime.i have checked hoses and clips right through to pump and found no issues.ihave water making it's own way to pump inlet.i can get it to work perfectly if I disconnect outlet pipe and suck it then reconnect to heat exchanger problem comes when I turn engine off.when I start her up again I have to repeat sucking process.i have found a very slight drip at back of pump but not enough to cause system to drain in such a short space of time.any help appreciated thanks guys

It only takes a very small air leak on the suction side to stop the pump from priming without assistance. In my experience that was a result of an imperfect seal on the lid of the water strainer.

 

[Plum]

ok thanks for your speedy reply.i have a spare pump but driveshaft to short.il take plate off that 1and try that today as they are the same pump.with different length driveshaft.i will let you know how I get on.thanks again

With the pump faceplate off put a straightedge across the pump to check the impeller is flush. Also check nobody has replaced the very thin paper gasket (assuming you don't have an o ring) with a thicker one trying to solve a leak.

 

[Kevin davis]

Something else for me to check on today.thank you m8.you could well be right as there is no seal on strainer but I will make 1 out of rubber mat I have down boat.i thought it just had to be tight enough to stop leaks.

 

[Kevin davis]

With the pump faceplate off put a straightedge across the pump to check the impeller is flush. Also check nobody has replaced the very thin paper gasket (assuming you don't have an o ring) with a thicker one trying to solve a leak.

Ok will do today

 

[john_morris_uk]

Something else for me to check on today.thank you m8.you could well be right as there is no seal on strainer but I will make 1 out of rubber mat I have down boat.i thought it just had to be tight enough to stop leaks.

Our strainer(s) have an ‘O’ ring seal in them. I usually put a very light coat of Vaseline on them to stop them sticking.

 

[vyv_cox]

Worn shaft seals can also introduce air into the pump. I had a similar problem, water drained out of the suction line after long periods of sailing, after which the pump would not prime. Shortly afterwards the seals began leaking. Replacing them solved both problems.

 

[UK-WOOZY]

when i got my boat in 2017, the pump didnt prime it was a worn cam, got a new waterpump in the end.

 

[Kevin davis]

Worn shaft seals can also introduce air into the pump. I had a similar problem, water drained out of the suction line after long periods of sailing, after which the pump would not prime. Shortly afterwards the seals began leaking. Replacing them solved both problems.

 

[PetiteFleur]

I found that a good smear of vaseline on the thread of the strainer cap fixed all my problems with not priming. I also made a wooden 'lever' to tighten the lid(and loosen it !) Works well.

 

[Kevin davis]

Thanks mate I have noticed that the seal at back of pump was not sat in its seat so put that back in might be the problem but won't find out as I've now found a leak on my sump so been stripping everything out ready to lift engine to change gasket.such fun.thanks I'll get sump done then jump back to pump

 

[Kevin davis]

One more question guys I've looked at faceplate for wear and there is some.would it work if I just turn it around the other way so the outside of plate is on inside just to prove a point?

 

[vyv_cox]

One more question guys I've looked at faceplate for wear and there is some.would it work if I just turn it around the other way so the outside of plate is on inside just to prove a point?

Yes you can do that provided there are no.name stamps on the outside. Alternatively you can flatten the wear by grinding with wet and dry papers on a glass plate

 

[Halo]

If it’s a a Vetus see through top strainer I would start with that.
The top expands and shrinks a lot with temperature ( general issue with plastic). Others have said about using Vaseline to help o ring seal. I also put a rag on top then pour on some hot water to warm the top. It then goes on much better and seals nicely. Trick also works for removing.

 

[Daydream believer]

If it’s a a Vetus see through top strainer I would start with that.
The top expands and shrinks a lot with temperature ( general issue with plastic). Others have said about using Vaseline to help o ring seal. I also put a rag on top then pour on some hot water to warm the top. It then goes on much better and seals nicely. Trick also works for removing.

Better to pour boiling water on to an old tea towel & hold that over the cap.It retains the heat more evenly & for longer. Same system for removing stuborn hoses from tails.