[DeTomaso] Fuel Pump Question

[Art Stephens]

     Thank you Doug and Jack for the explanation. I think I got the going 
lean part.  Hypothetical situation,  I have my car on a chassis dyno running 
wide open for a few seconds.  Fuel pressure does not drop.  That would not 
necessarily mean that I'm not at risk of going lean,  would  it?  If I am 
using fuel faster than the system is providing it,  could my gauge still be 
showing full pressure until the bowl actually empties?  I'm a little 
concerned about getting a false sense of security by watching the gauge for 
the brief time the car is wide open on the dyno.

Art



----- Original Message ----- 
From: "Doug Braun" <doug at silicondesigns.com>
To: "Art Stephens" <artstephens at charter.net>
Cc: "DeTomaso Forum" <detomaso at realbig.com>
Sent: Thursday, July 12, 2007 9:44 AM
Subject: Re: [DeTomaso] Fuel Pump Question


> Art,
>
> The richness of a carb's mixture is dependent upon the level of the fuel 
> in
> the float bowl.  Any reduction in the bowl level leans out the mixture
> because the venturi effect has a harder time sucking fuel out of the bowl
> through the jets.  If the fuel pump can't quite keep up with the demand, 
> the
> fuel level in bowl will fall and the engine will run lean.  You're correct
> that if the bowl level falls far enough the engine will die but the danger
> is that the fuel level falls but not far enough to kill the engine.  You 
> can
> check for this by reading your spark plugs right after a hard run, by 
> using
> a fuel pressure gauge that you can read under wide open throttle or a
> wideband O2 sensor.  I chose to mount a lighted Autometer fuel pressure
> gauge on the passenger side engine cover that I can read in my rear view
> mirror.  This also tells me when my fuel filter is getting too dirty.
>
> Doug Braun
> blue 73L #5505
>
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com
> [mailto:detomaso-bounces at realbig.com]On Behalf Of Art Stephens
> Sent: Wednesday, July 11, 2007 5:34 PM
> To: detomaso at realbig.com
> Subject: [DeTomaso] Fuel Pump Question
>
>     While running at wide open throttle and emptying the fuel bowls,
> wouldn't the engine just die instead of going lean?  It seems that it 
> would
> die and then briefly start up as the bowl started to fill and then die 
> again
> repeating the cycle as long as your foot was still in it?  Maybe you would
> be lean for an instant,  but then it dies?  If it was running that bad, 
> you
> would likely do something different and not continue to run it like that. 
> I
> guess if the pump was just a hair short of supplying enough fuel,  it 
> could
> theoretically give you a lean mixture that would make it go like hell
> without going so lean that it stumbles?
>
>
>
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