[T3] so it was 60 last friday

[Jim Adney]

On 22 Feb 2011 at 20:56, Keith Park wrote:

> I have an extra backflow valve in line with the pump that Jim Adney gave me
> after he rebuilt the pump, and after discovering that this eliminated the
> pressure falls

Keith had some trouble with the pump as I originally rebuilt it. 
Since then, I have taken greater pains to get a good finish on the 
Teflon buttons I machine for the internal pump check valves. I had 
expected the Teflon to cold flow and seal without this, but that 
didn't happen fast enough in Keith's case. I think there's a good 
chance that the extra check valve isn't necessary by this time.

> I really suspect that adding this valve might eliminate some of the
> flat spots some of us have with the D jet, and eliminate the hard
> starts that seem to be occurring From vapor lock or the pump losing
> prime. 

Neither check valve has any effect once the engine is running. The 
pumps deliver MUCH more gas than the engine can possibly use. This 
keeps the check valves open all the time. The excess gas passes thru 
the pressure regulator and back to the tank. Much more flows back to 
the tank than ever gets used.

Gary Forsmo did some tests on pump delivery rate. I don't recall his 
results exactly, but I think they were something like 3/4 liter per 
minute or about 1/4 gal/minute. If you traveled at 100 mi/hr and used 
gas at that rate, you'd be getting about 6 mi/gal. Having done 100 
mi/hr in a Type 3, I can assure you that the gas mileage is at least 
3 times better than that, even at 100 mi/hr.

Gary, correct me if I'm way off on your pump delivery rates.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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