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Re: Mechanical Fuel Pump Observations...
Posted by: jjohnsonjo ()
Date: March 09, 2018 10:14AM

I think the amount of tension and the force it takes to move the diaphragm itself is part of the equation. It doesn't seem reasonable the a an impregnated fabric diaphragm would be the same as a non fabric. The thickness, rubber durometer, memory, elasticity are all part of the final fuel pressure.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

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Re: Mechanical Fuel Pump Observations...
Posted by: MattNall ()
Date: March 09, 2018 10:16AM

That's why I just cut coils on the spring I have until I get close to 3 psi.





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 09, 2018 11:22AM

Century Spring has a $300 set-up fee.
Unless we can find a spring in stock somewhere...
I'm not so good at searching, perhaps someone could find something close to the parameters above.
I have an inquiry into another spring company.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: rick4130 ()
Date: March 09, 2018 11:40AM

I just keep reusing the "good spring" from an old pump that gave me many years of Service!

Rick MacDonald
'63 700 Sedan

rick4130@yahoo.com

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 09, 2018 04:18PM

Jim,
This is great data - thanks! The more I ponder this, the more I think I might make up a way to have an adjustable spring tension in my pump. I'm thinking a lead screw with a "plunger" that holds the top of the spring, and I can screw up/down to adjust its overall length, and use a lock nut. From here I can dial in a discharge pressure. However that would be a selfish solution unless I went into the fabrication business for replacement pump covers with this feature (and a corresponding spring).

I'm just getting home from work, and need to unwind a bit, but I hope to get into the garage later tonight and at least pull apart my new pump for inspection. A bourbon with my dog, in front of the fireplace in a well-worn chair are my duty station for a while... smiling smiley

Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: jjohnsonjo ()
Date: March 09, 2018 04:23PM

kenzen Wrote:
-------------------------------------------------------
> A bourbon with my dog, in front of
> the fireplace in a well-worn chair are my duty
> station for a while... smiling smiley
>
> Ken

Nothing wrong with bourbon, but a single malt scotch works better for me. Just ask me dog.

Cheers

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: Mechanical Fuel Pump Observations...
Posted by: MattNall ()
Date: March 09, 2018 05:38PM

Oh you Kids!!





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 11, 2018 07:38PM

Clark's Fuel Pump Inspection
As I mentioned earlier in the thread, I ordered a new Clark's fuel pump. Based on the discussion/claims in the Clark's catalog, Cal has done some work directly with the vendor to get this pump right. Interestingly, they do not disclose who the pump vendor is - the pump came bare in a typical zip-lock bag with the Clark's part number on the outside.

Observations:
1. The pump had a tag on one of the screws with "4886 34/17". 4886 is the part number, and I'll assume it was made on the 34th day of 2017. The pump is therefore relatively new from a manufacturing date. It also has "Made in the USA" on top.

2. Inspecting from the sides, the gasket material was thin (1/16" or so), and had black fibers running through its center. Given the manufacturing date from above, we can assume the gasket material is appropriate for exposure to modern gasoline.

3. The body screws have combination hex head and flat-tip screw driver heads. I noted the screw tension as delivered was inconsistent across the screws, although none I would consider "loose". The screws also did not go all the way through the pump base, leaving a couple unused threads in the pump base. I consider this a deficit - another 1/8" of length would have been appropriate to fully engage and leave a few screw heads exposed.

4. I measured the extension of the push rod from the base bottom: 3/16", which is just in the 1/8" to 7/32" spec.

5. Disassembling the pump, I first noticed that contrary to older pumps I have, and per my earlier recommendations in this thread, the pump gasket surface on the base and at the top (including the diaphragm surface) were machined flat, providing an optimal seating surface for the gaskets. However, this was not done on the center body part (where the check valves and intake/discharge connections are), but there was slight evidence of a quick "sanding" maybe to debur or deflash casting flaws. Prior to reassembly, I did take 220 adhesive sandpaper to a flat table top (i.e. cast iron band saw table) and clean up the gasket surfaces. I cleaned this up with spray carb cleaner. While doing this, I did note appreciable variation in the flatness of the top of the center body part, especially around the intake check valve. This could be a significant contributor to the pump internally leaking and dumping gas into the engine. See picture of variation during surfacing.

6. Upon disassembly, I did note the presence of fine particulates, apparently metal, "sprinkled" all over the inside of the pump. (See picture of gasket) Given how clean we desire our fuel systems to be, this industrial hygiene shortcoming should be addressed. This may have been from the observed light sanding I mentioned above. I could clean it up from the metal parts with carb cleaner, but the particulates were impregnated to the rubber gaskets and wouldn't come off. My concern here is how this could effect the check valve seals.

7. The check valves were each staked twice, 180 degrees apart, by a rather broad (3/32" or so) staking. I thought this was unusual from most which used a rather narrow staking. One concern is that having the two broad stakes 180 degrees apart, it squeezed the valves slightly out of round. I don't expect this to be a problem, and I don't think they will come loose either, however I'd recommend a 3 stake approach with a narrower stake as an improvement.

8. The diaphragm was a thicker material than the gaskets, and seemed to be of high quality material and fit/finish.

9. The free length of the diaphragm spring was noticeably shorter than the others I have. And somewhere the paper where I wrote the length down is in my garage (ugh), but I do have a picture to compare the springs attached. The tension of the Clark's spring (shorter one in picture) was beyond my scale capacity to measure, but the shorter length spring "by feel" was noticeably less than the longer spring.

From here I reassembled the pump with all the original parts, performing only the sanding on the inner body section to flatten the gasket surfaces.

Onto installation and road test.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 11, 2018 07:59PM

Installation and Testing of the Clark's Fuel Pump:

Attached is pictures of the pressure gauge rig on the bench, and installed. I ordered a 0-15# gauge to maximize the accuracy around the pressure ranges I expected to measure.

Bottom Line: The Clark's pump without modification to the spring sat at around 6.5# at fast idle (see picture), and once warmed up and at <1000 RPM speeds, sat at 5.5#. I'll call this "success" since this is only 1/2# above spec.

I have to spend some time with my carbs now since I rebuilt them over the winter, but due to my leaky fuel pump (which prompted this thread), I haven't been able to tweak/rebalance them until now.

With respect to the Clark's pumps, I feel it's essential to dismantle them and sand/surface the middle body section, as well as clean up the inside of the metal dust I found. I'm also going to get longer screws for the body, and put nuts on the ends to keep them in place. The spring and resulting output pressure I'll call "ok" out of the box, but I'd like to get the pressure down below 5#, closer to 4# or even slightly less. I'm not going to be playing with this for a while. I'm still going to figure out what an ideal spring tension would be, and the Clarks spring is a good starting point.

I hope some find this useful.

Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: toms73novass ()
Date: March 12, 2018 03:09AM

Great job!smileys with beer

-Tom


63' Monza Spyder Convertable (in process) MY Build Thread
73' NovaSS 454 Big block
86' BMW 325es
98' Dodge 2500 12v Cummins Diesel with 1200 lb torque!
98' VW Jetta TDI, for daughter
01' Audi Allroad Stage 3 twin turbo

NFCC
Grand Island, NY

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 12, 2018 03:57AM

Kenzen, what is the free length of the spring?

Also I wonder about the manufacturing date. "Everyone" was out of mechanical pumps last year and then all seemed to get some in at about the same time.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 12, 2018 04:03AM

JimBrandberg Wrote:
-------------------------------------------------------
> Kenzen, what is the free length of the spring?
>
> Also I wonder about the manufacturing date.
> "Everyone" was out of mechanical pumps last year
> and then all seemed to get some in at about the
> same time.

Jim,
I wrote it down, and then "put it down somewhere". I may have to pull the cover off and remeasure the spring. I do plan to stuff the other spring I have into the pump and measure the pressure as well now that I have the gauge installed. I'll dig for it this evening.
Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 13, 2018 05:35AM

The best original springs were ground flat. Looking at the springs above, I have to wonder about prying apart the bottom coil and grinding the top side of the end with a flat disc so it contacts well at the juncture. I suppose grinding the bottom flat would do the same thing.

When looking at Century Spring tapered springs, "closed end" and "closed end ground flat" were two different selections.

When checking spring rates in the drill press, some springs just didn't look like they came down evenly and I had to wonder how they would look in operation.

Another thing I thought I can do is determine the operating height of the spring when installed. I could measure the difference with the spring in the pump with the cover on loosely vs. pushed down to the base. That distance subtracted from the spring free length should be it, roughly anyway. A person could then check the weight of a spring at that level for comparison. It would be like the arbitrary 7/8 we started with but with a little more meaning. Good for our comparisons but not necessarily for looking for an in stock spring form a spring company.

I feel like Sheldon Cooper and Howard Wolowitz working on spring theory.

As an aside, my new 20 year old test pump that was putting out 10 #s but went to 4 #s with a short spring has begun leaking like a sieve out the back at the gasket. I've run it less than an hour.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 13, 2018 09:42AM

"Another thing I thought I can do is determine the operating height of the spring when installed."

This is where I came up with the 7/8" measurement reference. 7/8" is the height of the cap from the gasket surface. It may not be exactly the height, but its close.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: joelsplace ()
Date: March 13, 2018 02:51PM

Super information. Thanks!
One thing that I didn't see mentioned is that cutting the spring makes it stiffer while decreasing the preload.

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Re: Mechanical Fuel Pump Observations...
Posted by: MonzaJPD61 ()
Date: March 13, 2018 07:20PM

Why did GM change from the early style fuel pump/rod combination to the later design combo?

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 14, 2018 04:22AM

In another thread there's a cut-away of the pump. The bottom layer is called a "pulsator diaphragm". What does that do? Apparently it's more than just a gasket.

What usually fails that allows gas into the crankcase?

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: oldqmguy ()
Date: March 14, 2018 10:00AM

JimBrandberg Wrote:
-------------------------------------------------------
>
>
>
>
>
>
>
> I feel like Sheldon Cooper and Howard Wolowitz
> working on spring theory.
>
>
>
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com

Jim,

I almost had a heart attach laughing my 'rear end' off!!!! hot smiley

I hope you have better luck with "spring theory" than they do with "string theory!" grinning smiley

Dale cool smiley

Dale E. Smiley CPBE
Life Member The Society of Broadcast Engineers
RETIRED Broadcast Engineer
CERTIFIED CORVAIR NUT
CORSA/Circle City Corvairs/Corvair Performance Group
Avon, Indiana
WB9SFF
1967 4-Door Monza PG!

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 14, 2018 04:09PM

JimBrandberg Wrote:
-------------------------------------------------------
> In another thread there's a cut-away of the pump.
> The bottom layer is called a "pulsator diaphragm".
> What does that do? Apparently it's more than just
> a gasket.
>
> What usually fails that allows gas into the
> crankcase?
>
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com

If I remember correctly from my deep-dive into the CORSA tech library, it provides a damping function to smooth the pressure fluctuations of the discharge pressure. Note, the pump oscillates at the engine speed (3600RPM is 60Hz).
Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 15, 2018 05:30PM

For those of you tracking this, I bought a 25# digital scale, and from John Sweet an NOS fuel pump spring. I'm going to develop graphs of the spring tension profiles.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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