<VV> Healthy pumps?

Jack Kean jkean at sbcglobal.net
Thu Jul 17 16:22:53 EDT 2008


corvairs wrote:
> Jack - This current hysteria about fuel pump pressure is an internet red 
> herring.  Mechanical pumps have put out that kind of pressure all along. 
> (or at least, it is within range). Are you having problems that have 
> lead you to look at pump pressure?  By the way (to you guys who said 
> that the valves don't regulate the flow of fuel under pressure) how then 
> does the stock Corvair system "shut itself off" (stop fuel flow) when 
> the carb bowls are full or when the secondaries are closed?    Lon
>
>
> www.corvairunderground.com
>
>
> Jack Kean wrote:
>   
>> I inserted a fuel pressure gauge in the fuel line, in place of one of 
>> the secondaries in my 140 hp yesterday. It was registering around 8 
>> pounds at idle, 9 pounds per square inch off idle. Seems at least double 
>> the numbers listed in the shop manual. I am not sure of the source of 
>> this mechanical pump, since it was on the car when I purchased it. I 
>> will be looking into a fuel pressure regulator, which I will be able to 
>> continue to use if I chose to change to an electric fuel pump.
>>
>> jack kean
>>
>>   
>>     
>
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When I completed the rebuild of this engine last year, one of the first 
problems that I encountered was fuel dripping into the carburetors. This 
was occurring on both of my primaries (recently rebuilds from Grant 
Young). Grant worked with me, and after replacing one of the 
carburetors, we decided to lower the float level. This worked most of 
the time. In the mean time, after reading a number of these threads, I 
removed the top coil in the fuel pump. But I was always curious to see 
what the pressure was (after reading all of the threads), and so I 
placed the gauge onto my engine. No hysteria. I not running around with 
my hair on fire. I was simply curious to see what the pressure was. That 
being said, and my results being obtained, I can only reference the 
statements on page 6M-27 of the shop manual which state "/If pump is 
operating properly the pressure should be between 4 and 5 lbs. and will 
remain constant at speeds between idle and 1,000 rpm. If pressure is too 
low or too high, or varies materially at different speeds, the pump 
should be removed for repair or replaced/". Regardless, this pump seems 
to be exceeding the factory specification by almost 100%.

I was experiencing problems, that appear to be a result of high fuel 
pressure. I corrected the problem, and seem to have verified the root 
cause. If not, I would be curious to know why the shop manual is in 
error (not that this is a perfect publication). I would also be glad to 
hear the response to your question about how the fuel pressure is 
regulated.

thanks for your response.

jack kean


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