[DeTomaso] Fuel Pump Question

[Doug Braun]

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?