Jabsco Pump trouble

[chamac]

I have a Volvo MD22L engine with a Jabsco sea water pump driven off the camshaft. The pump was reconditioned about 50 hours ago. After about 40 hours the pump failed. I dismantled it to find the drive dog on the back of the camshaft and the slot on the pump completely worn away. I had the parts built up with weld and machined to fit into each other. This was a get me home repair. I dismantled the pump last week to find the parts very worn again but still intact. I assembled the pump with the proper Jabsco gasket and impeller and found it very hard to turn the pump (using a bar in the slot). If I take the end plate off I can see the impeller protruding about 1mm out of the case. So when the end plate is screwed on the impeller is somewhat compressed laterally. Is this normal? I thought about using a thicker gasket to relieve the friction. Maybe this would impair the working of the pump. Does anyone have experience with this problem?

 

[ipw]

when i repaired my pump i machined the back of the pump because it it was worn plus machining the flange were the cover goes to get the measurement back. This could have hapend on your pump . Using a thicker gasket will overcome your problem.

 

[TheBoatman]

Is there a possibility that during the repair the pump shaft has been forced forward so that when you fit the impeller it can't fit back down inside the pump housing?

The impeller should only just protrude - enough to make an airtight seal under the front plate - 1mm sounds excessive to me.

Peter.

 

[VicS]

[ QUOTE ]
If I take the end plate off I can see the impeller protruding about 1mm out of the case.

[/ QUOTE ] That's the cause of your present problems.

The Boatmans suggestion that the repairs to your pump could be preventing the impeller fitting correctly is one possible explation but if that was the case there will be a gap behind the impeller and the pump will not work.

Is it possible that you have got the wrong impeller? If it is going all the way to the back of the housing and is still 1mm proud then it is certainly not the right one for the pump.

Is it possible that your engine has the wrong pump fitted with the result that although you have the "correct" impeller for the engine your are trying to fit it in the "wrong" pump.

With the pump off and the shaft removed check the depth of the impeller with the depth of the housing. It should only protrude by an amount equal to the thickness of the gasket.

 

[chamac]

Thanks for your replys. I contacted Jabsco and got a reply in about 15 minutes. They say that the parts are correctly matched. They said that the pump would be very difficult to turn by hand and that it may have been damaged before it was reconditioned. There is .5 mm difference between the casing and the impeller. I think what I will do is repair the drives, put in an extra gasket and refit the pump. I will fit a Sureflo pump or similar nearby as a standby pump. If the mechanical one fails I have the electric one to fall back on. I can buy three electric pumps for the price of a new mechanical one.

 

[rogerthebodger]

Check the alignment of the pump with the drive dog in the cam shaft. I have a simular on my BMC and the same arrangment is used on the perkins 4/108 and if the drive dog in not concentric with the cam shaft it will wear the drive dog very quickly

 

[chamac]

Roger
The guy from Jabsco mentioned that too. I assumed that the drive mechanism would be OK since its bolted together using the original holes. One would assume that these were drilled in the right place by Perkins who made the Volvo block. I have time now so I will investigate it. Looking at the wear on the slot this might be the answer, its a bit to one side.