Re: fuel pump ponderings

From: Patrick Delgado (dadoctah@vitelcom.net)
Date: Fri Oct 15 1999 - 14:48:04 EDT


Any change in pressure on the pump's suction *will* directly change
the discharge pressure. e.g. If the full tank is 1' tall and adds .5
psi to the pump, it's discharge pressure would go from say 39
psi(empty) to 39.5 (full). However, the fuel pressure is maintained at
the fuel rail by the pressure regulator on older daks and the computer
on the newer ones so your pressure at the injectors goes unchanged.
If there is a difference, it is more likely being caused by the
different fuel temps. The cooler fuel is denser.

A point to ponder; the emission control system purges vapors from the
fuel tank, the purged vapors are the "lightest", most volatile
components of the gasoline. Therefore, the longer these vapors are
purged, the more "diesel-like" the fuel gets. Comments anyone?
Dr. Pat
----------
>From: Mike Crumley <mcrumley@airmail.net>
>To: dakota-truck@buffnet.net
>Subject: Re: DML: fuel pump ponderings
>Date: Fri, Oct 15, 1999, 5:11 PM
>

> At 11:35 PM 10/14/99 , you wrote:
>>I've consistently noticed that when I fill my gas tank after it is
>>nearly empty, I feel a significant increase in throttle response. So
>>much so, that I notice it without even looking for it. It stands to
>>reason that the cause for this is that the added pressure exerted from
>>the column of gas above it gives the in-tank fuel pump in our daks a
>>nice boost.
>
> Alternative explanation: Since the fuel pump is cooled not only by gas
> going thru it but also by being submerged in gas, as you run the tank below
> the 1/4 full mark the pump begins to heat up and pump less efficiently.
snipped>>>
> Mike Crumley 97 V6 Auto
> mail to: mcrumley@airmail.net
>
> "If we don't succeed, we run the risk of failure."
> --J. Danforth Quayle



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