From: John Stewart-Smith (micdunn@ev1.net)
Date: Sun May 02 2004 - 07:37:54 PDT
> I try to never let either truck get below 1/4 tank and try to keep them
> full. I have been told that if vehicle is throttle body you should not
run
> below 1/4 tank because fuel keeps in tank pump cool, if you run much below
> 1/4 tank you shorten life of pump.
>
> Everette
Everette makes a good point, and it is one that I have also heard many
times. Most fuel-injected (throttle body and multi point) gas engines use a
high pressure cylindrical pump that is submersed inside the gas tank. The
pump is kept cooler by the fuel. Logically, if you consistently run with
very little fuel in the tank, the pump would not last as long due to higher
operating temperatures.
I am writing this e-mail because I have replaced 3 pumps in different
vehicles in the last 6 months. In my Chrysler Jeep, the pump was just
hanging towards the bottom of the tank and sucking through a strainer. It
definitely was not cooled by gas below a quarter of a tank.
In my 93 GM Suburban, it was a similar setup.
In my 2000 GM LS-1, GM got pretty smart. The pump is enclosed within a large
plastic tube. The bottom of the tube has a hole and a strainer to suck gas
up from the bottom of the tank. The top of the tube is always kept full from
excess returning gas coming from the fuel filter. This means that the pump
is always submersed in gas as long as there are at least two cups of gas in
the tank.
How can you tell which design you have without taking the tank apart?
Simple. When you first turn the ignition on (without starting) there is
usually a two second loud buzzing noise from the pump pressurizing the
lines. If the volume of this buzzing noise increases greatly when the tank
is almost empty, your pump is no longer submerged and you have the older
system. Best if you don't allow the fuel to drop too low.
-Sarge
PS. mandatory MV content: My M35 starts and runs very well even if the fuel
pump fuse is removed, go figure.
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