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  #61  
Old 01-22-2019, 05:32 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
Join Date: Mar 2005
Location: Calgary, Canada
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Default Walbro Autopsy

Ok, I found a few minutes today to get my pipe cutter out and slice open a Walbro GSL 393 pump returned by a customer a couple months ago.

I first checked to be sure it didn't pump and it didn't, as he had said. Motor ran nicely with no unusual noises but no pumpy. This is the first Walbro failure I've seen first hand after using and selling these for 20 years. (hundreds). I had another customer report 2 failures after only a few hours but he'd mounted the pumps vertically with the suction end facing up, which is a no-no.





The pump is quite well made inside and as Otis reported earlier, these are not roller vane types as I have read elsewhere but in fact a gerotor type which is probably a better design for run dry scenarios. The gears are hardened ferrous material riding inside the black housing which is slightly magnetic but appears to be some sort of graphite/ metallic composite material (just guessing).



You can see Walbro went to some lengths to balance the motor armature- nice touch for longevity. On the inlet side, they have a fine plastic mesh screen of large area to prevent trash from getting to the gears. Another nice touch so they don't rely on external filters or tank socks solely to keep debris out. Good to know.



There is a pressure relief valve (white plastic button in photo). I believe these are set to relieve at 110 psi.



It's solidly constructed and has long brushes. It's a nice design IMO. As I said before, I had one of these on our shop car for 19 years and maybe 5000 hours. No issues.

Now the strange thing here is, I couldn't find anything wrong inside this pump. The drive tangs from the motor shaft engages the inner gear holes, nothing was slipping on the shaft, all the other shims and gaskets were intact and can't spin as that stuff is all held in place with the two Torx screws. I'll have to take a better look when I get some spare time.

Not shown in the photos is the aluminum outer pump housing the magnet housing above slides into.

Always interesting to see what's inside a mechanical device.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 01-22-2019 at 05:40 PM.
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  #62  
Old 01-22-2019, 06:13 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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I don't know if it's disappeared with the change in ownership, but both sales and technical pages on the old Walbro website were quite explicit on the GSL series being gerotor pumps.
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  #63  
Old 01-26-2019, 05:17 PM
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Hartstoc Hartstoc is offline
 
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Location: Sebastopol,CA
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Quote:
Originally Posted by rv6ejguy View Post
I'll try to find time to cut open this bad 393 I have here and post a photo. I'm curious about what's inside too.
Ross- THANK YOU for the photos- they are most helpful! The reduced parts count alone argues for the georotor over roller-vane types, so I’m greatly encouraged.

I’m really looking forward to thorough bench-testing of the GSL 395, because it would yield 35-45% greater range on battery power than the 393, but that will be my #2 choice. I’m tied up with other projects for a few weeks but will report back on my findings. I’m almost tempted to install one of each, but that would probably preclude operating them simultaneously for fear of inadequate flow through the 395 for cooling. On the other hand, it would be pretty easy to lockout simultaneous operation with a pump selector switch.- Otis

Ps- I’ve decided to cut up one of the Delphi’s pictured in my original post and will add photos of that to the collection we are building here- O.H.
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Last edited by Hartstoc : 01-26-2019 at 05:22 PM.
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  #64  
Old 01-30-2019, 06:00 PM
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Hartstoc Hartstoc is offline
 
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Location: Sebastopol,CA
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Default Another pump option and a new insight-

From what I can tell, the GSN Walbros are indeed the gold standard for in-line pumps for RV?s. Ross Farnham mentioned another Walbro model in a PM, the GSN 414, which looks even more promising than the 395 I?ve been considering as a solution to the most electrically-efficient choice for bendix-type FI aircraft. The performance chart I?ve seen for it, shown below, is clearly flawed as pump curves are never straight lines, but encouraging enough to have ordered one so I can bench test its performance. If the chart is even close, This pump holds the promise of well under 3 Amps continuous consumption at 25 PSI, which would really boost range after an alternator failure vs the 4.5-5Amps of the Delphi supplied by AP. It evidently also produces respectable flow at pressures that could even work with some EFI systems. I?ll be comparing performance of the Delphi, a Walbro GSN395, and the Walbro GSN414, measuring current and flow rates at 25, 30, and 40psi at three different fuel temps, and will publish the results in a new thread in a month or so. I?ll also disassemble all three because I plan on torturing them a bit as well, disqualifying them for installation on an airplane.


The insight came from pondering the built-in relief valve Ross pointed out in the 393 above. I talked again to the tech advisor at TI Automotive. I was able to determine that all of the GSL?s have them, and their purpose is to prevent them from self-destructing in a no-flow condition when mounted in-line in vehicles without any means of returning fuel to the tank. They are set to the maximum rated pressure for each pump and simply shunt fuel internally back into the non-pressurized side of the pump section.

This is OK up to a point, but it would never be a good idea to rely on this for an airplane, which still require return lines like those coming off Ross?s regulators or off my external relief valves. They certainly would not tolerate operation with zero throughput for long without damage, and this relief valve would never actually open at all in a properly equipped aircraft. I suspect that any regular use of the built in relief valve would shorten pump life, as it would get hot in there very quickly at zero or near-zero throughput and the high-amperage that would be required to activate the relief valve.- Otis
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RV-7A (bought)
Built Monnett Moni
Frmr Test Pilot/Author CAFE APR's:
RV-8A, S-7C, Europa, Glastar.
-2019 VAF donation!!-
"RV-Fun is inversely proportional to RV-Weight!"
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  #65  
Old 01-30-2019, 06:35 PM
rv6ejguy's Avatar
rv6ejguy rv6ejguy is offline
 
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The current draw would be so high at the pressure relief setting that I think you'd blow the 10-15 amp fuse/ breaker in a few seconds anyway. They are just there to prevent immediate destruction if flow was stopped for some reason. At some point, the motor would stall due to load. That wouldn't be a good thing either.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #66  
Old 07-24-2019, 09:16 AM
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charosenz charosenz is offline
 
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Location: Longview, Wash
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Default walbro gsl393

Someone mentioned he could not find the GSL393 on the walbro site and wondered if it had been discontinued.

it is still listed for on the website, here is the linke.

https://walbrofuelpumps.com/walbro-g...fuel-pump.html

Excellent thread thanks to Otis for doing this and for all the contributors!

Charlie
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  #67  
Old 07-24-2019, 09:34 PM
SteveR SteveR is offline
 
Join Date: Dec 2006
Location: Hudson Oaks, TX
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I installed one of the Airflow Performance pumps from the OP last year. The pump may be good, but the wire terminations that came on the pump were trash. One of the crimps failed after 50 hours flying time simply from loosening the pump to check the filter. The wire pulled out of the crimp. The 2nd wire pulled out with very little effort. The terminals were about the cheapest you can buy, WalMart quality. The crimps appear to have been made with pliers or something else entirely unsuited for the job, and with no attention to quality. My mistake for not checking them. Airflow Performance should simply leave the leads off the pumps. If you have the leads, throw them in the trash. I can't believe they used these on a $900 pump.

Last edited by SteveR : 07-25-2019 at 04:42 AM.
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  #68  
Old 07-25-2019, 09:32 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by SteveR View Post
I installed one of the Airflow Performance pumps from the OP last year. The pump may be good, but the wire terminations that came on the pump were trash. One of the crimps failed after 50 hours flying time simply from loosening the pump to check the filter. The wire pulled out of the crimp. The 2nd wire pulled out with very little effort. The terminals were about the cheapest you can buy, WalMart quality. The crimps appear to have been made with pliers or something else entirely unsuited for the job, and with no attention to quality. My mistake for not checking them. Airflow Performance should simply leave the leads off the pumps. If you have the leads, throw them in the trash. I can't believe they used these on a $900 pump.
Something odd here. You buy it directly from AFP? Cut away the heat shrink to see the crimps? Got photos?

I'm pretty sure Don would want to investigate, and the rest of us are curious.
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