Walbro fuel pump disassembly

[joff]

Arizona Rotary Rockets donated a walbro fuel pump recently to me for destructive disassembly. The pump was out of a car that had experienced fuel system glitches. There actually didn't seem to be anything wrong with the pump, but Glen told me it will never go in a AZRR car because it can't be known for sure due to the circumstances in which it was replaced.

Anyway, some background on the pump before I post pictures.

The pump is covered under US patent #4500270 and the number is stamped right on the metal cover. http://www.freepatentsonline.com/4500270.pdf for full text of the patent. The patent includes many technical illustrations and detailed descriptions of the operation of the pump. The patent was published in 1985 and is now expired and free.

Abstract:
"A positive displacement fuel pump utilizing an in-line pump and armature with a flexible drive connection and spring-pressed backing plate for the pump and short cantilever mount shaft for the pump rotor."

This design is more similar to our oil pump (positive displacement) than our water pump (centrifugal). Or -- another way to look at it -- more similar to a twin-screw supercharger than a turbocharger.

There is a spring loaded one-way check valve in the plastic fuel outlet barb to keep pressure in the fuel system for faster starts. The check valve includes a very small spring and rubber gasket.

There is also a pressure relief valve that only allows maximum pressure to avoid hydro-locking the positive displacement gear pump. The pressure relief valve is a spring and rubber ball. The pump vents excess fuel to a port on the top of the pump.

The motor is a regular DC motor with spring loaded carbon brushes and commutator.

Size comparison with cell phone:
5688

Bottom plastic piece removed -- gear rotor showing through opening
5689

Metal cover removed
5690

Top plastic piece and rubber o-ring
5691

Top plastic piece pulled apart, showing brushes and brush springs
5692

[joff]

Flexible fiberglass like diaphragm (theres another one inside the motor housing)
5693

Top plastic piece and misc parts in background. Check valve is visible on outlet.
5694

Cut out the check valve to see what it looks like -- just a spring and piece of rubber.
5695

Cut out the pressure relief valve. Bigger spring and rubber ball.
5696

Motor connected to the gear-rotor.
5697

[joff]

Little gear rotor pump assembly is pretty neat. Made of stainless steel.
5700

Look what I found in a corner when I was at AZRR -- 2 20B's waiting to be rebuilt and ported!

5698

Saw this on their shelves too. Somebody's having them build a drag car. Yes, that turbo is actually bigger than the housing!

5699

[joff]

Compared to a turbine (westco) pump like the Bosch 044 this pump design will inevitably produce more small pressure fluctuations due to the positive displacement design. It also has a few more failure points with the fiberglass diaphragm and pressure relief valve and integrated check valve.

The motor is a brushed motor, which means it has a finite lifetime and inevitably will wear out. The gear rotor has metal/metal contact and will also probably wear out (or seize). The electric motor has no ball bearings -- it is held upright by raw plastic/metal contacting "pegs".

Here's the patent on the westco pump:
http://www.freepatentsonline.com/3233551.pdf

It is my understanding that the Bosch pumps use this basic design but packaged in a more appropriate way for a fuel tank. Reading the more recent NipponDenso patents and Bosch patents it seems only very minor improvements have been made from the 1966 design. (Mostly regarding pump channel and the water wheel aerodynamics)

[RETed]

Just to play devil's advocate...

Do you know what the predicted life cycles of the fuel pumps are?
I mean it's one thing to argue certain parts are inferior (that's obvious), but what if it was perfected fine give certain operatin parameters?
Are you qualified to make those conclusions?

Also, if it isn't obvious, there are lots of Chinese fakes out there.
Can you confirm if the unit you've got is a true Made-In-USA unit?


-Ted

[joff]

Just to play devil's advocate...

Do you know what the predicted life cycles of the fuel pumps are?
I mean it's one thing to argue certain parts are inferior (that's obvious), but what if it was perfected fine give certain operatin parameters?
Are you qualified to make those conclusions?

Also, if it isn't obvious, there are lots of Chinese fakes out there.
Can you confirm if the unit you've got is a true Made-In-USA unit?


-Ted

Its not my intention to argue whether or not this pump is inferior to anything else. I've tried to only present facts.

I am an electrical engineer and not making any conclusions. Brushed motors are known throughout the industry as not as long lasting as brushless. Wikipedia can even confirm this. At this point, I don't even know if other pumps use brushed or brushless motors.

This pump is not bad. Some positive to balance out what may have unintentionally been seen as negative:

*) The brushes seem long -- there is lots of spare length in the upper pump housing. Not certain how much life this pump has seen and what length the brushes started so I personally could not predict lifetime. If I dissected a brand new pump, I could measure brush lengths and give a percent used-up on this one.

*) The diaphragm's seem made of fiberglass. These material is flexible, yet very sturdy.

*) The patent is newer.

Its not obvious to me there a lots of Chinese fakes, I only have this one to compare. I try to do my own research on things rather than follow hearsay.

As to whether or not this is a true made-in-usa unit, please take a look at this pic:
5701

[RETed]

Check this page out on fake Walbros:
http://www.fuel-pumps.net/walbro-forgeries.html

There's a lot of other web pages out there, and it's easy to punch in "fake walbro fuel pumps" into a Google search.

This is not hearsay.
It's been know for a few years now.


-Ted

[joff]

Check this page out on fake Walbros:
http://www.fuel-pumps.net/walbro-forgeries.html

There's a lot of other web pages out there, and it's easy to punch in "fake walbro fuel pumps" into a Google search.

This is not hearsay.
It's been know for a few years now.
-Ted

Interesting. Thanks for the links!

Anybody have internal pics of fake vs. real walbros? That link is surprisingly sparse of what I would call real evidence of inferior quality. It basically says, "if its cheap, its likely a fake" and as for how to determine whether its fake: "get a vendor promise" -- sounds more like a vendors emotional marketing appealing to patriotism than actual scientific evidence of quality.

Don't take this the wrong way, but hearsay is information gathered by Person A from Person B concerning some event, condition, or thing of which Person A had no direct experience ("he said she said"). All I meant is that I have no direct experience with fakes, what may be sufficient evidence to you of conspiracy is just hearsay to me.

Maybe Glen at AZRR can respond to the origins of this pump. Walbro's probably just a phone call away too. I have no problem giving them a call and seeing whats up.

[glenrx7]

On the origins of this pump they are not clear. The fd it came from was a customers car about 3 years ago. I believe it is a real walbro. The car was having all kinds of issue fuel related and we have to rewire the entire fuel system. We decided at the time to pull the pump and go back to stock due to the situation. I do not believe there was anything wrong with the pump at the time. The car was being sold and turned out the main issue was a map wiring issue. from my experience this is a real walbro it did not have the turkey gobble or some of what looked like poor build quality (chinese just have a odd looks).

Jesse, weather your doing this with a chinese pump or not great data and sweet research.

I am a 044 fan myself but have used and continue to use walbros.

[glenrx7]

Little gear rotor pump assembly is pretty neat. Made of stainless steel.
5700

Look what I found in a corner when I was at AZRR -- 2 20B's waiting to be rebuilt and ported!

5698

Saw this on their shelves too. Somebody's having them build a drag car. Yes, that turbo is actually bigger than the housing!

5699

By the way That turbo is a holset and it is going on the azrr drag r100.

[joff]

Another interesting thing to point out is this particular pump's gear rotor is not exactly the same as the patent diagrams. If you read whats actually in the "claims" section, there is no mention of number of teeth or shape of teeth which is something where they differ. There are several other slight variances between patent and actual implementation that could possibly be the result of whats done for different size pumps and/or subtle improvements or reductions in cost through the years. It could also be places where a generic and brand-name walbro could differ.

It seems the "Walbro" name may be on a similar track as the "Westco" name. Both used to be a company name, but now almost more appropriately refer to a type of pump design, that without patent protection, is easy for just about anybody to manufacture.

Here's a link to a Westco style, or "Turbine" pump -- its not a fuel pump, but the PDF has an informative breakdown of the guts of what makes it work.

http://www.mepcollc.com/1484.pdf

[joff]

I got a response from Walbro corporate on the authenticity of this pump. Turns out Glen was right and this pump is genuine.


From what engineering can tell from the photos, it appears to be ours.

There are many off-shore counterfeiters. They will also copy “made in USA”, our model numbers, even our manufacturing date code information not knowing what it is. From the outside, it is sometimes very difficult to tell ours from a counterfeit.

For a reliable source, you can contact our national distributor, The V E Petersen Company @ 800-537-6212 or online through Cyberspace Automotive Performance at www.Fuel-Pumps.net.

Hope this helps you and thanks for asking.

Regards,
Diana Hutchinson
TI Automotive Aftermarket
630 Columbia Street
Caro, MI 48723

dhutchinson@us.tiauto.com