<VV> Electric Fuel Pumps

[tony..]

If you have a turbo car you may run into some issues with the current 
crop of mechanical fuel pumps.  That 4-5 psi may overpower the fuel 
inlet valve on a typical Carter carb on Spyder/Corsa turbo engines, 
causing a rough idle, bad fuel economy, poor throttle response, sooty 
tailpipe, and in general a dissatisfying automotive experience that 
results in uncomplimentary bad language.   And, the car will run like a 
3-leg'ed dog.


Turbo engines seem to enjoy around 2.5-3 psi.  Any higher pressure than 
that becomes problematic.  Been there done that several times.

  I "fixed" one Spyder by dismantling the fuel pump and cutting off a 
short section of the spring (about 1/4 turn or thereabouts) as a stopgap 
to drop fuel pressure since that spring determines the working pressure. 
     This likely needs to be a calculated step since snipping too much 
off the spring might cause it to get "lazy" at higher rpm, possibly 
cause the engine to drain the carb faster than the pump can keep it 
filled and start to run lean. Under boost.  At high rpm.   Bad.  Don't 
let that happen.  Most people buy one of those nifty little fuel 
pressure regulators (Clarks) that allow you do dial in the pressure you 
want... which can be done by "ear" simply by reducing the fuel pressure 
until any rough idle disappears... IF excess fuel pressure is what's 
causing the very high mixture with the corresponding rough idle.


After the fact and all that having been said, if I run across another 
instance of too much fuel pressure I'm likely to break out the torch and 
heat a section of the spring to allow it to be shortened about a 
half-inch rather than cut it.  Again, likely a trial & error sorta thing.


tony..


On 4/12/2024 2:08 PM, Bryan Blackwell via VirtualVairs wrote:
> Hi Fred,
>
> I have an Airtex E8016S on a 110, as far as I know all the late model pumps are the same for all engines.  FWIW, we've spun the 110 to 6k with this pump feeding it, no issues.  It's rated at 2.5 to 4.5 PSI and 30 GPH.
>
> The shop manual says 4 to 5 PSI and 1 pint in 40 seconds, that translates to 11 GPH.
>
> Based on the above, I'd expect that Airtex to work fine on any mostly stock Corvair engine.
>
> --Bryan
>

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