Here's my opinions:

Fuel pump timing... not sure what you mean by this. If your talking
about the time the fuel pump engages when you turn the key... with the
engine not running... then the answer is the computer is handling that.

I think the main reason for having the pump in the tank... cost.

As for different pumps for basically the same vehicle. The only reason
I could think of is that car manufacturers are always making revisions
to parts... attempting to improve them. The different pump in this case
may be an improved version of a previous pump. Remeber that the
improved version may or may not be backward compatible with previous
versions due to mounting bolts...etc. This is one of the major reasons
that application data is so vast at auto stores.

www.telstar-electronics.com

The pump need engine input to the computer that says the engine is
running, pump away.  Otherwise it times out.

Turn your key from off to run and you will hear the pump start up.  It
then will shut off.  That is how long it takes the computer to time out.

As far as the rest goes, they wanted to make it very complicated and
difficult to replace the fuel pumps solely with the purpose to make the
mechanics that fix them money.

The old external electric and mechanical pumps were too easy for the
average joe to get, get at and fix.

Total planned obsolescence at it's finest.

The new pumps are cooled by the fuel coming back the return line going
into a jacket around them so they can make cheaper pumps and more
complicated seeming systems to 'snow job' the average consumer some
more.

The first generations of external pumps even had brushes you could
replace....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)

Fuel pumps are normally controlled through a relay and few seconds
'cycle' .   With the key on, the pump is engaged.  If no engine
movement (not running, sometimes no oil pressure, sometimes high
engine temp) is detected, the pump is disengaged in usually 2-3
seconds.   This 'timer is part of the Engine Management System
(computer).

The pump in the tank may be a cost saver or not.   The advantage of a
submerged pump is it runs cooler and quieter with out suction leaks.
Replacing the pump may be less than an advantage.

Interesting question and I have no answer, except for possible fuel
types and fuel pressure requirements for different engines.

It's interesting that Ford makes this distinction between gas and
alcohol fuels.   It may mean that they are ahead of the pack with
different fuel pump seals/impellers/designs to accommodate the
emerging fuels.  On the other hand why not supply  all Fords with this
capability as a cost saver.  Any difference in pump parts cost would
be more than made up in   -  less part numbers/ stockroom space, a
single production line, certainly less logistics in production and
distribution.   This one is difficult to understand because Ford
traditionaly  spends a nickel not a dime.   Or maybe someone is
stringing you a line.

In article
<1146058999.719659.302050@e56g2000cwe.googlegroups.com>,

Yes.
A circuit in the PCM pulls the fuel pump rely control circuit to
ground, the PCM pulls the relay control circuit to ground if;
1) it senses the ignition circuit power up from off.
2) There is an RPM signal from the ICM.

Fuel under pressure is less likely to vapor lock or foam.

The 126" pump uses a steel top flange, the 118" pump uses a
plastic top flange, there are also differences in the plumbing.
Apparently there is a marked difference in the design of the fuel
tank/system between the two wheelbases.

Indeed, the flex fuel pump would need certain material upgrades
if it is to survive the higher alcohol blend.

The ECM (engine control Module) has circuitry that provides the ground for
the fuel pump relay. That circuitry contains a timer circuit that only lets
the pump run for a couple of seconds if there is no rpm signal recieved from
the engine.

Less expensive to make a pump that does not need to provide lift ( suction
to pull gas from the tank).

Fuel tank configuration is different on different wheel bases. Therefore
pump design varies.

Different pump construction materials are needed to handle the corrosive
properties of extra methanol

Timer? There is no timer for the fuel pump.

It's actually cooled by the fuel surrounding it. External pumps are cooled
by fuel going through, but internal pumps are cooled by fuel surrounding
them. Obviously there is a certain amount of cooling by the fuel passing
through, but the pump is submerged, and that's where the primary cooling is
accomplished.

That's a good question. I'd guess that the tank is different on different
wheelbase trucks, but that's only a guess.