Fuel pump

[Tom Cloud]

        [ snip ]

>I have always heard that keeping the in-tank, low-pressure pumps to feed
>the high-pressure fuel injection pump was a good idea, but now I am
>beginning to wonder.
>Since fuel in the fuel injection systems circulates, there is a much
>higher flow-rate than with carburetor systems that must only fuel what
>the motor needs at the moment.
>Could it be that the pumps that are designed for carburetors can't keep
>up, and thus they burn out?  Then the lack of decent flow can in turn
>burn out the fuel injection pump?  Maybe the fuel injection pump is
>fighting even a good low-pressure pump and thus burns out?
>I have figured out that MY (maybe not yours) low pressure pumps will
>only pump to their capacity and no more (even if you try to "suck" more
>out of them.)  I figure this because if you unplug the power from them
>and remove the fuel hose, not a drop will come out, even with a full
>tank.  I think this would definitely put a strain on the high pressure
>pump if the low pressure pump could not keep up with its capacity.

Tom, the pumps I'm familiar with are "gerotor" types.
I.e. they are like oil pumps .... not impeller types, and
they seal pretty tightly -- that's how they manage to
build up pressure.  That's also why you can't suck any
(or not very much) through them.

I installed the Holley ProJection and had no problems,
until I started having problems  ;-)   My Bronco was
stalling after driving for awhile.  Holley replaced
the pump (I had a fuel pressure gauge on it and it showed
low pressure when I stalled).  The new pump worked great
for a day or so and then it was back to the same ole same ole.
Then I installed a Holley Red pump (actually a Holley LOUD
pump) before their supplied Carter inline pump.  That
made it go farther before it stalled.  I finally disassembled
the whole danged system -- including taking the gas tank
and the pickup off.  Checked the pickup filter sock.
It looked okay, but I replaced it anyway.  That was the
only thing I hadn't replaced .... it worked great ever
after that.  [I later put the old sock in gasoline and
it appeared that there was something on it that swelled up
in the petrol and clogged it slightly.]

All that to say that I believe I'd be okay with the
single Carter pump -- though the output pressure is
definitely more stable with 7 psig input rather atmospheric,
and several books I've read about the Holley system suggest
putting the Holley red in front.  But, I also think you
have noted a distinct possibility that when one fails
it could cause starvation in the other and subsequent
failure of it also.

Tom Cloud <cloud at peaches.ph.utexas.edu>