[Shotimes] lost MPG due to fuel pump?

[Kevin & Cheryl Airth]

Erik:
 Seems to be a lot of confusion here!
 When the car is started from a cold state the fuel injectors give a ultra
rich fixed mixture of 2:1. For a warm start condition (115F and above) the
fixed fuel mixture is 12:1. So you are much more likely to "flood" the
engine from a dead cold start condition (Less than 115F engine temperature).
Ford considers -20F as cold-cold and 115F as warm-cold. Note: The EPA
considers 68F as "cold".
 This rich mixture is fine if the engine starts but if it does not, you will
soon be flooded. You can get too much fuel when the IAB is not opening
enough or when you don't have good enough spark/ignition problems or other
things. When you keep cranking the engine, the PCM will cut back the
injectors after 20 seconds. I have not been able to find out if they are
shut off or just reduced? The PCM assumes the engine is over-rich and needs
more air and less fuel.
 Now if you hold the accelerator pedal down the system enters the
"De-Choking" mode.The fuel injectors are cut off completely as the engine
try's to dry out the plugs and cylinders of excess fuel.
 The IAB is fully open during engine cranking and supplies 100% of the air
to the engine but has to close somewhat quickly and dynamically to regulate
the idle speed after the engine has started. Note that cranking and starting
are two different conditions! So your IAB might open fine and allow the
engine to start but if it is sticky even a little bit the car might stall or
run rough until it warms up some. I think this is why most SHO's have a RPM
run up at start. The IAB can't react quick enough to control the engine
speed. Mine usually goes to 2500 RPM and then settles down to the proper
speed.

I don't think this would impact your mileage but am not sure. Have you
changed the fuel and air filters?
.
.




> Just curious as my ongoing problem continues...is it possible for a weak
> fuel pump to reduce the MPG of the car by 50-60 mpg per tank?  Just
thinking
> about when I had problems starting the car.  It wouldn't start due to the
> fact it was either flooded or from lack of fuel.  Anyone know what happens
> to the SHO when you floor the gas pedal on startup.  Does it cut the
excess
> fuel from entering or does it add more fuel upon startup?? My next step is
> to find myself a fuel pressure gauge and take some readings.  Thanks
>
> '95 MTX
> masho95