Jabsco not pumping.

Guys
I’m helping my neighbor work on his 6KW NL generator. His original impeller failed/ came apart and he installed one from his stock (was on the hook). It never primed up. He installed a second one with the same result.
I helped him look at it yesterday, confirmed all components prior to pump were fine.
I spun the engine over, plate on, and held my finger on the suction side and there is no suction.
WTH

The seacock is open, right? How difficult is access to the seacock? Maybe remove the hose from the seacock and hold it up and fill it with water to give the pump positive water flow and see if it primes.

Take the plate off and with the thruhull closed, bump the engine over to see if the impeller spins. The spline on the pump could have failed.

All of the above is good advice. Sometimes old impellers from stock develop cracks at the tip of the vanes and won't pull a prime. Open the impeller cover and squirt in some dishwashing liquid like Dawn to help seal the cracks. Then give it a try.


David

If you grease the inside housing and end plate before installing the impeller, it helps seal and gives the pump more suction power. It also protects the impeller from heat damage while running w/o water on first start.

Be sure that o-ring is the right size. It looks awfully thick to me. If it’s sized incorrectly it will leak air and the pump won’t develop suction.

Thanks for all the great reply’s. Larry, I thought the same and actually removed the plate and shot a video of it spinning but couldn’t figure out how to post it here.
I pulled the impeller that was installed (The first was NOS, second was purchased locally), inspected the condition of the back plate on the pump. It looked fine. The inner shaft seal appeared fine. Shouldn’t there be a huge suction when spinning over?

Did you remove the original o ring before you put in the new one? Seen that happen. Up close

As long as you know the impeller is spinning, and the cover is sealed, it will pump, even with a bad shaft seal. You probably have an obstruction in the inlet or outlet plumbing. You could have something covering the inlet, the heat exchanger blocked, etc. A plastic bag over the inlet will keep some pumps from working.
When I was running military boats with jet drives, a plastic bag against the jet inlet could stop the pump from moving water at idle.

You said his previous impeller "came apart". Did he get all the pieces out of the heat exchanger? It could be so clogged with those parts (plus the parts of all the previous impellers that have been used until they "came apart") that no pump can push water thru it any more.

Strainer outside of hull clean?
Sea strainer inside boat clean?
If intake hose is off and you open the seacock, does water come out?

Why did original impeller fail? Burn up? Break up? old age?
Did you account for all of the broken pieces?
The slightest air leak will prevent lifting water up to the pump if the pump is above the waterline.
Liquid soap is good.

If the inside of the cover plate is worn, the pump won’t prime. If the front plate is worn, you can usuall just flip it over and re-use it.

inlet plugged, remove inspect and consider replacing if there are barnacle in the hose. Something about the hose if it had been plugged up with barnacles. Even if all removed, the inside of the hose it roughed up enough for the barnacles to grab hold.
Assuming the through hull is not plugged up, remove the hose on the inlet to the cooler. Remove the outlet and blow backward in the cooler. WE never know what the previous owner did or didn't do. Happened to me, blew back through the cooler and pump. LOTS of little pieces came out of the hose. Shame on the previous owner.
Also check the seawater strainer cap's o'ring is still good.
Use wire reenforced hose.

All great suggestions everyone. To clarify,
I actually spun the engine over, with in/ out hoses removed. Thumb over suction side after removing and inspecting the new impeller. Used Dawn during installation. End plate had minor wear but I flipped it over anyway so the “new” face faced the pump. Spun engine over. Still no suction.
The new impeller has a round opening it the center. BTW, this impeller is not splined, it has a screw that is driven by a notched slot in the shaft. His kit didn’t have a “plug” for the center hole, as I have seen used on some pumps. I fashioned a new one, using the one from an old kit I had.
Assembled again and no luck still.
Initially he had installed the new gasket and o ring. I thought this may have caused the problem but that’s not the case.
help......

Put impeller in and install cover plate. Take a hose and blow into pump outlet (top). If you can blow through pump, pump body is either worn or impeller is wrong.

I have run into impellers that were like 1/32" shorter than they should be. Same thing, would not prime. I think they too were NOS and the rubber shrunk. Get some calipers and measure axial length.

Could he have removed the pump and installed it upside down?

From your test we can be sure the problem is with the pump.
Is the impeller turning? Broken drive screw?
Is the cam worn? If it doesn’t fold the blades enough, it won’t pump.
Is the back of the pump worn? You checked the cover plate already.

I kind of like Ski’s pressure test idea but I’ve never tried it.

Looking at the photos you supplied if the impeller is spinning counter-clockwise the suction is on the top. If that is the way it is supposed to be fine. If not rotate the pump 180 degrees and try again. The vanes spread to suck and squeeze to discharge.

I agree

hmason said:

Be sure that o-ring is the right size. It looks awfully thick to me. If it’s sized incorrectly it will leak air and the pump won’t develop suction.

Click to expand...

This is a thicker oring than the one that comes with my impellor

These impellers must rub on the ends. Or, there will be no pumping.

hmason said:

Be sure that o-ring is the right size. It looks awfully thick to me. If it’s sized incorrectly it will leak air and the pump won’t develop suction.

Click to expand...

I think you’re onto something. That o-ring looks pretty big to me.
Diver Dave is right, the clearance between the end plates and the impeller is almost nothing. Most of this style pump use a very thin paper gasket.

My Jabsco 10970 once stopped pumping after an impeller change. Had me stumped for a week or so until I called Jabsco. The tech advised me to check the wear plate opposite the cover side of the impeller. I didn't even know there was a wear plate. I carefully pried it out and installed the replacement plate Jabsco sent to me for free. Worked like a champ!

He also mentioned the option of reversing the back plate to use the fresh side as the inside cover. He said the imprinted part numbers on the back wouldn't be a factor in the plate seal. I haven't tried that yet but am keeping it in mind if ever needed.

Looking at a closeup of the photo, it appears the impellor isn't set in the pump cavity all the way. That, combined with wrong o-ring and it'll never prime.

More great replies. I like Ski’s test method. I also need to confirm the complete pump wasn’t removed and the installed correctly. Will look into o ring size and rear plate as well. Update soon-

The photo in this link may help: https://www.northern-lights.com/m673l3-65-kw/

Based upon what I see in the link (I should have checked this before commenting) and in your photos it is mounted properly but still worth double checking its rotation just in case. Seems like you have plenty ammo to troubleshoot with now...

Maybe sucking air somewhere. I had a similar problem . With the advice of a fellow TF member I swabbed heavy wheel bearing grease on every possible place it could be sucking air prior to the pump. I found my air leak , it was the cap at the top of the strainer.The oring was hard so I replaced it.
If a connection is sucking air it will suck the grease in and seal .

FYI, there are boxes of 400+ O rings in a vast range of sizes to be found on Ebay. I splurged $18.50 for the allegedly oil/fuel resistant version. No excuse for not having the right size at hand.

I hope they came in more than one box.

diver dave said:

I hope they came in more than one box.

Click to expand...

In one oblong purpose designed hard plastic box. Sizes from tiny to 53mm, I was after the 10 deck fill size O rings, but some of the rest some will be handy.

a defective impeller, wrong o'ring, you expected it to pump?

Thanks all for the support.
Dock neighbor updated me and it’s “fixed”. The solution was reported to be a check valve installed past the pump. (This hose initially had an anti siphon loop).
I know.
This leaves many unanswered questions for me. But he is understandably proud of his results-