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Weldon boost pump leaking a little...solutions?

MacCool

Well Known Member
At the current condition inspection, my A&P/IA noted a little blue staining below the electric boost pump on my RV-9A with IO-320D1A. He was hoping it was a fitting, but he now tells me that it looks like it's leaking through the motor.

The pump is an 11 year-old Weldon A8163-A, mounted on the firewall lower left corner.

Solutions? Replace the pump with a rebuilt/overhauled pump? Replace with new? If so, who do I get to rebuild it, or what pump do I replace it with?

Thanks


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That’s a bit of an unusual pump to see in an RV, but a very quick Google search shows that Aircraft Spruce carries overhauled/exchange units. Definitely not cheap, but not exorbitantly so if you decide to go with a more standard pump and have to pay a mechanic to re-do the plumbing and mounting to make the new one fit.

Paul
 
Yeh, looks like I can buy a new one direct replacement for $1250. What about getting this one overhauled, or buying an overhauled version? Any concerns about installing an overhauled/rebuilt boost pump? Or is a new one a more prudent choice? Not looking to cut corners, but not looking to waste money either.
 
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Shouldn't the drain (from a leaking pump seal) be at the 6 o'clock position? This should allow any leaked gas to drain before entering the motor. The pump still needs replacing; I've been through this with a very similar Dukes pump on my Cardinal and they weren't cheap 20 years ago......
 
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I appreciate the input. I'm new at this. I ordered a rebuilt Weldon A8163-A pump from QAA. $890 rebuilt as opposed to $1250 new, and ships today.

Walt's comment about this pump being mounted on the firewall is intriguing. This pump only has about 360 hours on it. I like having it under the cowl instead of in the cockpit, but it may well be that the heat in there, on a pump that already tends to run hot, is detrimental to longevity. Obviously it doesn't actively run much, but still...
 
Also, these pumps are usually mounted with the motor vertical. Not sure, but wonder if the horizontal mounting might be related to the prior leak...
 
exhaust hangar

As mentioned in another thread, you may want to have a look at the exhaust support. I know some have gotten away with hanging them from the engine mount, most recommend suspending it from the engine, due to the "wet dog" shaking at startup and shutdown. If you are not sure about how much they shake, get a tripod and video it with the cowl off or even with it on focusing on the exhaust - it moves a surprising amount.
 
Also, these pumps are usually mounted with the motor vertical. Not sure, but wonder if the horizontal mounting might be related to the prior leak...

I asked about that. Both Weldon and QAA say orientation doesn’t matter. Horizontal is fine.
 
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I have sent several Mooney boost pumps (I'm and IA) to Aeromotors to have rebuilt. The charge has always been $350. They have stc'd differrent more modern materials that should last longer. The pump wil sound different when you get it back.

http://www.aeromotorsllc.com/aeromotorsllc/

I’m already committed, but good tip for next time, thanks. Aeromotors advertises a rebuild of that 8163A for $400. I found a couple of places that would overhaul the pump for $850, or sell a rebuilt one for $880 + core, which is the option I chose. A new one is $1250 at Spruce and most places. They also offer rebuilds, but didn’t have any in stock, and IIUC QAA supplies their rebuilds anyway.

I’m already wired, plumbed, and mounted for the Weldon, so that was my choice. My IA recommended that the plane shouldn’t fly, so the time frame at Aeromotors would have been a little problematic, and they don’t take credit cards or Paypal.
 
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Not sure mounting on the forward side of the FW was such a great idea though, really should be on the cool side.

Would it be reasonable to put consider a duct and blast tube down there on the lower left cowl?
 
I appreciate the input. I'm new at this. I ordered a rebuilt Weldon A8163-A pump from QAA. $890 rebuilt as opposed to $1250 new, and ships today.

Walt's comment about this pump being mounted on the firewall is intriguing. This pump only has about 360 hours on it. I like having it under the cowl instead of in the cockpit, but it may well be that the heat in there, on a pump that already tends to run hot, is detrimental to longevity. Obviously it doesn't actively run much, but still...

Heat for the longevity of the pump is not the main issue with an under-cowl mount. The pump has a large surface area and will absorb heat and transfer to the fuel. It just means that your mechanical pump sucks hotter fuel and will lower the ambient temp at which cavitation would occur. Also the temperature inlet to your boost pump is elevated. However, if you have an acceptable operation method for always using the pump for TO and Landing that has not yielded pressure issues, then you should be good. My tunnel (7) heats the fuel anyway.

i.e. - if it is working for the full operating envelope of temperatures and conditions, don't fix it.
 
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Heat for the longevity of the pump is not the main issue with an under-cowl mount. The pump has a large surface area and will absorb heat and transfer to the fuel. It just means that your mechanical pump sucks hotter fuel and will lower the ambient temp at which cavitation would occur. Also the temperature inlet to your boost pump is elevated. However, if you have an acceptable operation method for always using the pump for TO and Landing that has yielded pressure issues, then you should be good. My tunnel (7) heats the fuel anyway.

i.e. - if it is working for the full operating envelope of temperatures and conditions, don't fix it.

Valuable input, thanks. The boost pump is only used for priming, take-off, and landing, and fuel pressures are always nominal. Never runs for more than about 3 minutes (annunciator/timer).
 
As mentioned in another thread, you may want to have a look at the exhaust support. I know some have gotten away with hanging them from the engine mount, most recommend suspending it from the engine, due to the "wet dog" shaking at startup and shutdown. If you are not sure about how much they shake, get a tripod and video it with the cowl off or even with it on focusing on the exhaust - it moves a surprising amount.

I appreciate the observation. Exhaust on both sides is supported by brackets that attach both on the engine and on the engine mount.
 

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