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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 04, 2018 05:47PM

JimBrandberg Wrote:
-------------------------------------------------------
> My buddy Fran Schmit looked into mechanical pumps
> a few different times. One thing he found last
> year when examining multiple pumps from various
> manufacturing generations is that the main body
> regarding the locating hole is inconsistent. Some
> folks talk about shortening the pushrod coming out
> the bottom of the pump if it's longer by measuring
> its protrusion but that isn't the whole story if
> the locating hole isn't consistent.
>
> It would seem the distance the pushrod pushes
> the diaphragm material would affect fuel pressure
> and fabric longevity, if it's opened too far and
> stretched it just won't last. Part of the equation
> is the locating hole and how much the diaphragm is
> opened with some preload when installed.
>
> Something I haven't done is make a point of
> installing the pump to the engine with the pushrod
> on the engine in the down position. Perhaps a
> fellow could develop a feel for the preload. It's
> hard to get much feel with two springs and all but
> maybe if doing it a certain way consistently...
>
> It seems like tightening the screws may be more
> of a function of compensating for poor metal
> surfaces. A lot of times they don't really seem
> loose and sometimes the cheap Grade 1 screws
> aren't up to much torque. A change to a quality
> screw would be a good thing.
>
> Fran Scmit worked a little with Dave Herron 15
> years ago or whenever that effort at a good pump
> was afoot. I remember discussion then that the
> attachment of the pushrod to the fabric was
> difficult to achieve, that the original AC tooling
> was difficult to duplicate.
>
> I appreciate your efforts and would love to see
> a good mechanical pump achieved. It doesn't help
> that there hasn't been consistency. It seems like
> the big problem in 1999 was gas in the oil; the
> big problem in 2005 was valves not staked, the big
> problem in 2014 is too much pressure... Of course
> that's way too general of a statement.
>
> I never have enough original springs and
> shortening and reforming seems sort of crude,
> maybe I'm not that good at it. Just having a good
> spring would help my efforts. I should start
> sanding the surfaces too.
>
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com

Jim - these are great observations. Do you have an old spring that you know delivers in-spec pressure? If so, could you measure its tension at 7/8" compressed height?

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 05, 2018 07:26AM

I have a pile of fuel pumps and parts which ebbs and flows. I didn't have an original spring last week, it could have changed but I don't think so.

How would I measure spring rate? I've used my neighbor's tester for suspension springs but have never done anything small. I have a device for measuring valve springs but I seem to get different results than the fellow at the Machine Shop, also it's not really for something that light.

I've got a scale for measuring rod weights, I wonder if that would work.
Maybe cut a nail to 7/8" like when doing valve shims, make a hat for the top of the spring and push it down with the drill press?

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 05, 2018 10:07AM

My brother is coming over on Thursday and he loves lab type of stuff. We can check some springs then, I must have an original one around here somewhere.

Is checking it at 7/8 enough? Is there an installed at rest length and installed compressed length so the difference between the two could be compared? Or maybe just a comparison based on 1" of travel? Even though it doesn't travel an inch is that what spring guys use to list "spring weight"?

I suppose wire diameter, number of coils and freestanding length are things to measure. I suppose it gets a little tricky when the diameter of the windings is not continuously the same diameter but they are similar in the progression. Number of coils is a little tricky since I suppose you don't start counting until the coil come off it's perch.

I suppose the more information the better and you can decide what's pertinent.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: jjohnsonjo ()
Date: March 05, 2018 11:45AM

>
> I've got a scale for measuring rod weights, I
> wonder if that would work.
> Maybe cut a nail to 7/8" like when doing valve
> shims, make a hat for the top of the spring and
> push it down with the drill press?
>
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com

The rod weight scale may not go high enough, a kitchen scale should get you pretty close.

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: kenzen ()
Date: March 05, 2018 06:07PM

I used a kitchen scale and compressed it with a short ruler. I had a lollypop next to the spring that just happened to be 7/8" in diameter. (this doesn't need to be precise, just ballpark). Since the oscillation is only slightly more than 1/8" (0.147), the tension variation wouldn't be much.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 06, 2018 07:07AM

I was starting an engine on the cart yesterday and installed a fuel pressure gauge. The pump I was using is new from about 20 years ago. My buddy Fran gave a few to me with a promise that I would only use them for emergencies, they are prone to leaking into the crankcase.

The pump was putting out 10#s of pressure. I started disassembling some old pumps and tagging the springs as to which pump they came from. There sure isn't much difference between a "good" original spring and a "bad" one with too much pressure.

I found an original spring that was very rusty when removed. I cleaned it up with a brush and coated it with a little grease before swapping it in. Pressure went from 10 to 3.5, I don'y usually see that much of a swing. I suppose with the rust the effective wire diameter is down fromm .090 to something considerably less. I would expect that the spring may fail but who knows.

So far I found 3 different spring lengths which I'll refer to as short, medium and long. I found short and medium length springs in AC Pumps. I'll wait to post about wire size and number of turns but they are surprisingly similar.

It would be nice to spend some more time swapping springs and testing pressure on the same engine, not sure I have that kind of time right now.

You said the spring only has about 1/8" of travel. Any idea what length relaxed and compressed the spring operates in? I suppose compressing to 7/8 and measuring is a good means of comparison.

Is there a spring catalog with abundant selections or are they special order in batches?

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Date: March 06, 2018 08:40AM

Using the new CORSA Tech Articles Search (Thanks Steve Spilatro!) I found a great discussion of the Fuel Pump "issues" that included comments from Larry Claypool, Steve Goodman, David Herrin, Lon Wall.

April 2001 Communique - available for download for CORSA members online.
Article begins on page 15.


Dan Davis ~ Pierce County, WA ~ CORSA Western Director + Corvairs NW + North Cascades Corvairs + Corvanatics
1966 Corsa Turbo coupe ~ ~ 1966 140 Corsa ~ ~ 1965 Monza 140/4 'Vert Sierra Tan/Fawn ~ 1964 Monza 'Vert (SOLD) ~ 1960 Monza Ermine White/Red PG ++ ~ 1965 Monza 140/4 Evening Orchid w/ ivory/black interior ~ 1962 Monza Wagon 102/4 ~ 1963 Rampside/Scamper ~ 1963 Red/Greenbrier ~ 1969 Ultra Van #468

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 06, 2018 05:49PM

>
> You said the spring only has about 1/8" of
> travel. Any idea what length relaxed and
> compressed the spring operates in? I suppose
> compressing to 7/8 and measuring is a good means
> of comparison.
>
> Is there a spring catalog with abundant
> selections or are they special order in batches?
>
> Jim Brandberg
> Isanti, MN
> CorvairRepair.com

Should be roughly 7/8 +/- 1/16"
Look at centuryspring.com under compression springs

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 06, 2018 05:50PM

1966-Corsa-GT-180 Wrote:
-------------------------------------------------------
> Using the new CORSA Tech Articles Search (Thanks
> Steve Spilatro!) I found a great discussion of
> the Fuel Pump "issues" that included comments from
> Larry Claypool, Steve Goodman, David Herrin, Lon
> Wall.
>
> April 2001 Communique - available for download for
> CORSA members online.
> Article begins on page 15.

Excellent - thanks!

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Date: March 07, 2018 03:03PM

Kenzen - You have my full support! Right now I'm too busy in the swamp to comment on this endless subject - but you're going about it in the right way.

Matt - I'll try and keep up on the discussion.

As with any issue my opinions are my opinions - right now - If anyone can find out different then that's great. One thing I currently believe is that the spring/pump pressure issue is a red herring. All it has accomplished so far is to convince people to take apart and tamper with thier new fuel pumps.

On ward!

Lon Wall

Fireman Sumpter Valley Railroad #3 and #19
svry.com
www.pacificmodelloggerscongress.com

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Re: Mechanical Fuel Pump Observations...
Posted by: blackspyder ()
Date: March 07, 2018 05:01PM

My suggestion is if you could find a pump that Dave Herrin, aka The Source, reproduced, I believe that Dana did them from the exact GM blueprints. Or to find an very early NOS pump that has the part number engraved on the top cover. This may help with your research. The only pump I have left from Dave is almost 30 years old and still works great.

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Re: Mechanical Fuel Pump Observations...
Posted by: jjohnsonjo ()
Date: March 07, 2018 05:43PM

Or, just contact Dave, he may have a few stashed.

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...
Date: March 07, 2018 09:27PM

The entire Dave Herrin fable should be discussed at some point.

I suggest speaking with Duane Wendland of Corsa Oregon first regarding "Revision 1" "revision 2" "revision 3" etc etc.

There are NUMEROUS mechanical Corvair fuel pumps that have worked over the years. There are also many that did NOT, including most of Mr Herrins. he MAY have given it a "good try" but he pretty much failed.

We should not continue to perpetrate the falsehood that his pumps were something special.

Lon Wall

Fireman Sumpter Valley Railroad #3 and #19
svry.com
www.pacificmodelloggerscongress.com

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Re: Mechanical Fuel Pump Observations...
Posted by: blackspyder ()
Date: March 08, 2018 04:02AM

I figured at some point Lon would have a response to my post about Dave Herrin.

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 08, 2018 05:56AM

I have a gauge to measure fuel pressure. 9 or 10 lbs. is too much.

I can reduce the pressure by disassembling the pump and swapping or modifying the spring. I would not waste my time doing this if not necessary.

I would sure like to find a solution to the mechanical pump problems and support someone making a good effort. I tried talking to Airtex tech two years ago to no avail. The fellow on the phone said 7 1/2 was within spec. That's too much for me.

Too much pressure is only one problem. Internal and external leaks are two more.

I see red herring described as misleading information to distract, not sure what that means here.


It doesn't help that the pump manufacturer can only be guessed at. I don't think anyone is selling a Corvair fuel pump made just for them in a special way. I could be wrong.

Kenzen you have my support as well and I agree you're going about it the right way. A proper spring and sanding the gasket surfaces seems like a good start for me although disassembling a new pump to fix it certainly rubs me the wrong way.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 08, 2018 04:37PM

I purchased a kitchen scale and did some measuring. I measured 4 springs that are basically 3 sizes, I would call them short medium and long. The long one was supplying 10 # of pressure measured with a tee in the line going to the right carburetor. I don't know if I'll have time to swap the springs into the same pump on the same engine for comparison.

I measured them on the scale as requested by kenzen @ 7/8". I also measured them at 1" which seemed more like a round number.
The number of turns listed is total, there's about 1 turn that is in contact with the base before it lifts off.

I've numbered and tagged them. 01, 02 and 04 are from ACs, 03 (the 10# one) was another brand. Now that I'm set up I can add to the list.

Spring #.... Free Length.... Wire size.................. #of turns......... lbs @7/8"............. lbs @1"
01.................. 1.85.................. .095.................. 4 7/8.................. 14.10.................. 10.13
02.................. 1.90.................. .092.................. 5........................ 15.10.................. 12.10
03.................. 2.10.................. .097.................. 4 3/4.................. 16.15.................. 14.13
04.................. 1.90.................. .093.................. 5........................ 15.15.................. 12.10

I've got several more of the long springs taken from pumps the last few years that had excessive pressure. I suppose I could measure some more of them to see if they're consistent. I also have several more pumps I can disassemble and check the springs if I can find some more time.

It's also difficult to be accurate. I used a 1/4" fender washer sandwiched between 2 nuts on a full thread bolt as an adjustable stop. I pressed down on it with the drill press and it's a little difficult to feel when the bolt contacts the bottom, of course you can keep pressing down once it contacts but I think I did okay.

Jim Brandberg
Isanti, MN
CorvairRepair.com



Edited 1 time(s). Last edit at 03/08/2018 04:59PM by MattNall.

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Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 08, 2018 07:51PM

Jim,
Great idea with the drill press - that will be my approach in the future This is interesting data in a few ways. First you correlated a 16/14 tension (7/8 and 1" compression respectively) to 10# discharge pressure. Second, (noting the first point) you captured a general trend that they are all to stiff to produce a 4-5# discharge pressure. Third, the 1/8" difference in compression varied spring tension 2-4#, which means the spring rates were also inconsistent and very sensitive for a small change in compression. Noting the rod is stroked about 1/8" by the crank eccentric, the tension variation can be almost as high as the discharge pressure spec(!). Also note the length of the pushrod spec I believe is +/-1/16", so that will shift the spring tension variation around by this magnitude as well. My gut tells me the current pump manufacturers (is there more than one?) are using a general spring they use for many pumps, and aren't too concerned about achieving our particular pressure spec.
I rec'd my new pump from Clark's and a 1-15# gauge as well. I have to buy some fittings to plumb up the gauge connection. Hope to get in the garage tomorrow night.
Thanks for your efforts!
Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

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Re: Mechanical Fuel Pump Observations...
Posted by: krfjkm ()
Date: March 08, 2018 07:59PM

Really interesting thread here---

KRFJKM
Charlotte NC
1965 Corvair Corsa

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 09, 2018 06:34AM

I went to Century Spring website and couldn't find anything to match. What we want is a tapered spring. I can try to get a spring weight which would just be the difference in 1" of travel.

I measured a "short" spring and came up with this criteria.

OD small end 1.225
OD large end 1.850
Free length 1.850
Wire diameter .092
#of turns 5
Closed and ground flat ends would be best although recent springs are just closed.
Spring steel unfinished.
There's some +/- room I think.

It's too bad they don't have something even close. I'd hate to commit to a run of custom springs if they came out unsuitable.

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Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 09, 2018 09:32AM

I went out to measure spring rate which is the difference during 1" of spring travel. I think a spring specification sheet just wants that figure, since the spring rate is linear as it's being compressed, I don't think they think in terms of what it is at a certain point. This is also easier to measure because 1" of travel is marked on my drill press handle.

Some of the information here is redundant so my previous post can just be discarded. Unfortunately I could find nothing close at Century Spring under tapered springs.

So my 4 springs tested are of 3 different lengths, I would call them short, medium and long. 01, 02 and 04 were in AC pumps. 04 was of unknown manufacture but the pump was putting out 10#s of pressure with that spring. It went to 3 1/2 lbs with a spring similar to 01 but rusted away somewhat, I would maybe guess 4 #s with the healthy 01 spring.

# Free Length Wire size # turns Small End ID/OD Large End ID/OD Rate

01 1.85 .095 4 3/4 1.14/1.22 1.67/1.85 12.87
02 1.90 .090 5 1/4 11.62
03 2.10 .091 4 3/4 13.50
04 1.92 .092 5 11.56

So I think a good spring might be
Free Length 1.85
Large End OD 1.85
Large End ID 1.67
Small End OD 1.22
Small End ID 1.14
Wire Size .090 - .092
Number of turns 4 3/4 - 5
Ground flat ends
Spring steel
Unfinished

Again I would hate to commit to a run of custom springs if they came out unsuitable. I'm not particularly skilled in this area. There might be other variables besides the spring in a fuel pump pressure output. There sure isn't a big difference in the various springs for how much difference it makes. Not compared to the whopping big difference when cutting a coil off and reforming the end. Also the nicest looking springs don't have an even look when compressing, the ones I've cut and reformed must look atrocious.

Jim Brandberg
Isanti, MN
CorvairRepair.com

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