Original Mechanical Fuel Pumps

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Amskeptic
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Original Mechanical Fuel Pumps

Post by Amskeptic » Fri Apr 10, 2015 11:48 am

A "more correct than Brazilian" Pierburg pump has now been installed on my 1600 singleport engine to see if I can clean up some horribly rich hot starts. This pump has a dedicated cut-off valve sitting on the top of the pump to prevent fuel migration up to the carburetor:

Image

No more Brazilian pump . . . and I have a rebuild kit that gives me peace of mind when hence I am in the middle of nowhere.
Image
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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hambone
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Re: Original Mechanical Fuel Pumps

Post by hambone » Fri Apr 10, 2015 11:58 am

So WHY NOT install the funky Brazil kit and shim the hell out of the pump? 30k miles on that setup 4-me. It's all the rest of the world is using...
Once these cars become the domain of high cost purists I'm outa here. They still must provide reliable and cost effective transportation.
Or, go straight to hell and run a modern Brazil pump. Our Bug has this setup, still running well after 7 years. It really comes down to the individual. I like to push my luck.
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
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Amskeptic
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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Fri Apr 10, 2015 1:42 pm

hambone wrote:No leakage.
So WHY NOT install the funky Brazil kit and shim the hell out of the pump? 30k miles on that setup 4-me.
BECAUSE . . . .
because it is not about output pressure that can only be partially tamed by "shimming the hell out of the pump" it is about the outlet, the outlet, the percolation, the hell of rich starts in Death Valley and Los Angeles, the outlet does not have the Pierburg CUTOFF valve that stops the percolation, the percolation, my god stop the percolation . . .
My Brazilian pump gave me 53,000 miles, yes, BUT we don't do . . . percolation
Colin
(that ranted, I don't even know if this pump is going to behave in the heat, yet)
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

71whitewesty
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Re: Original Mechanical Fuel Pumps

Post by 71whitewesty » Fri Apr 10, 2015 2:11 pm

I do like the look of that pump. Where did you get it? Cost?
I also just cleaned up a stock D pulley too and had no idea there was another size..
I learn so much here....Thank you. =D>

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Amskeptic
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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Fri Apr 10, 2015 2:59 pm

71whitewesty wrote:I do like the look of that pump. Where did you get it? Cost?
I also just cleaned up a stock D pulley too and had no idea there was another size..
I learn so much here....Thank you. =D>
I got it from Hambone . . . :flower:
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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hambone
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Re: Original Mechanical Fuel Pumps

Post by hambone » Fri Apr 10, 2015 5:56 pm

Bastard, I was wondering where that pump went. :blackeye:
Yeah I know I gave it to u freely.
Colin you worry too much. Burn thru VWs like Bugler! Drive til they drop!
BTW you only have to shim the German pumps with the rebuild kits. Stock Brazil new pumps seem to have the correct PSI. So if you shim a German pump, problem solved? Eh?
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
your brand new leopard skin pillbox hat

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Amskeptic
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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Sat Apr 11, 2015 7:15 am

hambone wrote:Bastard, I was wondering where that pump went. :blackeye:
Yeah I know I gave it to u freely.
Colin you worry too much. Burn thru VWs like Bugler! Drive til they drop!
BTW you only have to shim the German pumps with the rebuild kits. Stock Brazil new pumps seem to have the correct PSI. So if you shim a German pump, problem solved? Eh?
Hell, Bambi, I mean, Well Hambi, this rebuilt Hambone Commemorative Pierburg pump says "2.2 psi" on the outside of it in magic marker. The internal spring is the primary determinant of fuel pressure. I was about to get cranky anew until I thought "fuggit, all is lost anyway, just see what happens" and the big pressure gauge in the photograph said "2.8" and the factory requires "3-5 psi".
My Brazilian gas happy fuel pusher was at 4.4 psi and I had aforementioned floodiblubitidinously rich hot starts.

I could . . . erroneously join in with the clamoring and conclude that fuel pressure is the problem with hot rich starts, but I'd be wrong. The factory pressure is not about pressure! It is about delivery, boy, delivery. Pressure only insures Delivery. Delivery is volume. Volume is highest up around 4,000-4,400 rpm, and if the factory is to be believed, your long 3rd gear 45-50 mph hill pull in a Type 1 1600 bus **could suffer a lean out** that you would never even be aware of up in the cockpit, but your valves would know.

I am going to live with this low pressure because I expect that my Dakota Digital CHT gauge will inform me if I lose fuel delivery on that 16 mile grade outside of Baker CA . . . :pale:
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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Re: Original Mechanical Fuel Pumps

Post by kreemoweet » Sun Apr 12, 2015 12:30 am

So, that is the whispered-about Vintage Werks rebuilt fuel pump? Why is it so blue?
Amskeptic wrote: . . . the factory requires "3-5 psi".
Well, that depends on where you look. The 66-69 Type I Bentley manual, speaking of the very pump in question, says:
" . . . [at 3400 rpm] . . . Gauge should show pressure of about 2.8 psi". Minimum output is spec'd at 400 cc/min, also at 3400 rpm.
Absent some serious mechanical fault, it's hard to imagine how a fuel starvation situation could occur.

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Amskeptic
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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Sun Apr 12, 2015 8:14 am

kreemoweet wrote:So, that is the whispered-about Vintage Werks rebuilt fuel pump? Why is it so blue?
Amskeptic wrote: . . . the factory requires "3-5 psi".
Well, that depends on where you look. The 66-69 Type I Bentley manual, speaking of the very pump in question, says:
" . . . [at 3400 rpm] . . . Gauge should show pressure of about 2.8 psi". Minimum output is spec'd at 400 cc/min, also at 3400 rpm.
Absent some serious mechanical fault, it's hard to imagine how a fuel starvation situation could occur.
The '66-'69 Type 1 is a 1500 . . . :cyclopsani:

The 1600 singleport bus engine is the only upright engine allowed to run at 4,600 rpm (in 2nd and 3rd), that is why the bus engine had the higher fuel pressure (and the cast iron generator pulley . . . it has to hold together at a whopping 7,360 rpm and be ready to cruise all day at 6,176 rpm at 65 mph).

Note that the higher pressure on the bus pumps does not change the 400cc/min capacity, but it is tested at 4,000 rpm on the bus. German engineers, so precise and stuff.
Colin
(blue hue is strictly due to my ancient color-blind and rogue intermittent flash Kodak EZ Share camera guessing at aperture and shutter speed these days)
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

kreemoweet
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Re: Original Mechanical Fuel Pumps

Post by kreemoweet » Mon Apr 13, 2015 12:16 am

So are you suggesting that 400 cc/min delivery capacity is not considerably in excess of the fuel requirements for any normal kind of driving? If it is, then
would that not mean that any tut-tuting over lower-than-specced pressure rather misses the point?

I suppose you could increase the output pressure of your lovely "new" pump simply by installing a stiffer spring. Stiffer-than-original fuel pump springs
seem to abound these days. In my collection, the range of spring force is nearly 2:1, from 5.5 lbs to over 9 lbs at 12.5 mm (approx. max spring compression
with "normal" diaphragm pull rod length, in the square-top Pierburg pump you have). Say the word, and I'll send ya one of my Stiffer Springs, for free!

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Amskeptic
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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Mon Apr 13, 2015 7:33 am

kreemoweet wrote:So are you suggesting that 400 cc/min delivery capacity is not considerably in excess of the fuel requirements for any normal kind of driving? If it is, then
would that not mean that any tut-tuting over lower-than-specced pressure rather misses the point?
Well, you bring up an interesting point . . . beyond the definition of "normal kind of driving", we have the factory trying to cover "abnormal kinds of driving", like going up a hill. :cyclopsani:

Specified fuel delivery is 400cc/min = one gallon every 9.4 minutes (a gallon is 3,785 cc's).
Floored 3rd gear hill pull at 45 mph at 4,000 rpm 1600 bus = one gallon every fifteen minutes (11 mpg).
kreemoweet wrote: I suppose you could increase the output pressure of your lovely "new" pump simply by installing a stiffer spring. Stiffer-than-original fuel pump springs seem to abound these days. In my collection, the range of spring force is nearly 2:1, from 5.5 lbs to over 9 lbs at 12.5 mm (approx. max spring compression
with "normal" diaphragm pull rod length, in the square-top Pierburg pump you have). Say the word, and I'll send ya one of my Stiffer Springs, for free!
The Bentley Manual says to stretch the spring until you obtain specified pressure.
Believe it or not, folks, the pushrod length adjustment has more to do with volume than pressure. What shimming is really doing is limiting the stroke of the diaphragm. It is the stroke of the diaphragm that dictates the volume. The spring is what actually pushes the fuel to the carburetor.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

kreemoweet
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Re: Original Mechanical Fuel Pumps

Post by kreemoweet » Mon Apr 13, 2015 11:57 pm

Amskeptic wrote: The Bentley Manual says to stretch the spring until you obtain specified pressure.
Yes, it does. It also says to squeeze the spring if pressure is too high. I can't think of worse counsel: squeezing the spring does absolutely nothing. A "stretched"
spring is a broken spring. Stretching springs is an act of desperation.

I dunno about that pressure/volume thing. Seems to me there is no ying without the yang. The pushrod stroke is the determinant of maximum diaphragm
spring compression, which is another way to say "pressure". The volume delivered will just be whatever amount of fuel can squirt through the 1.5 mm orifice
of the carb needle valve, given whatever obstruction may be present at the moment at that orifice by the "needle".

With the Pierburg square-top pumps (the ones with the cutoff valve), there is the added complication that the fuel pressure must be high enough to open
that valve. I wonder if the higher pressure spec for the dual-carb bus is because it had a stiffer cutoff valve spring?

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Re: Original Mechanical Fuel Pumps

Post by Amskeptic » Tue Apr 14, 2015 9:34 am

kreemoweet wrote:I wonder if the higher pressure spec for the dual-carb bus is because it had a stiffer cutoff valve spring?
Have you ever spec.d out a hydronic heating system installation for a meadow mansion with sunroom?
I have.
The math involved with head pressure, every 90* fitting, the resistance of the zone control valves, the elevation from boiler to third floor, the heat-loss calculations of every window and door and roof surface area atop the insulation values of the top floor ceiling, the wall surface area, the climate zone curve for 90% of expected temperatures over the 20 year expected life span of the system, the calculation of delta T from the btu capacity of the boiler as it heats the volume of water necessary to fill the system, it is all a headache.
I support the factory's answer of the pressure required to supply two PDSIT carbs at the distance and installed elevation from the pump through two 5mm fuel hoses sprouting from a tee at the calculated maximum fuel consumption rate of the engine . . . dual carb engine 5 psi, late 1600 3-5 psi.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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hambone
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Re: Original Mechanical Fuel Pumps

Post by hambone » Tue Apr 14, 2015 11:28 am

How is that 2.8 PSI working out? I don't like it.
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
your brand new leopard skin pillbox hat

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asiab3
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Re: Original Mechanical Fuel Pumps

Post by asiab3 » Tue Apr 14, 2015 1:53 pm

hambone wrote:How is that 2.8 PSI working out? I don't like it.
Mine is working lovely around 2.5-2.8psi. I have not noticed any overly-rich hot starts, nor any spike in CHTs in long third gear climbs. I have not, however, climbed at 4,000 RPM for more than three miles at a time.

This same engine on my old dual port was run at 5psi for a long time. Hot starts were maddeningly rich, but I do think that there is more to it than JUST the reduction of fuel pressure. The new engine runs with the surface temp of the fuel pump, case, and carb/manifold cooler, so there is less boil-over due to heat. There is also a new needle valve in the carb, so I think bets there are off too.

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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