[Shotimes] lost MPG due to fuel pump?

[Jim and Debbie Leyden]

Kevin,
Thank you for an informative and well thought out response.  I would like to
add one small tidbit if I may.  I was told (by a certain SHO Guru) that when
the key is operated from the OFF position to the START position (as opposed
to from the ON position to the START position) that the PCM runs what I will
call the "START_SUBROUTINE".  The subroutine enriches the fuel mixture to
allow a faster start.  It is the same basic idea as the choke on a
carburetor engine.  I have tested this theory myself by trying both ways
when the engine fails to start on the first try.  If you merely turn the key
to start again, the engine will more than likely still be difficult to
start.  However, every time that I shut off the key and re-try to start the
car, it usually starts right up.  Furthermore, I was told by a VW mechanic
that is the reason the VW's (the older ones anyway, I can't speak for the
newer ones) had a mechanical lockout that required you to turn off the key
before attempting to start the car again.

Jim
'93 MTX


----- Original Message -----
From: "Kevin & Cheryl Airth" <clubairth@cajunnet.com>
To: "Erik Balser" <masho95@charter.net>; <shotimes@autox.team.net>
Sent: Tuesday, January 14, 2003 1:08 PM
Subject: Re: [Shotimes] lost MPG due to fuel pump?


> 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
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