Chris
regarding the action of the fuel pump I offer these general comments.
The pumps are based on displacement of a suitable "Piston". This is
generally a rubber diaphragm activated by a solenoid in the case of an
electric pump, or a lever arm off the cam on the cam shaft in the case of
mechanical (Stock) units. In all cases the displacement of any "stroke" is
small but the frequency (RPM) can be high. More like a vibration than a
stroke.
These pump strokes are controlled by a one way check valve that keeps the
fluid from being pumped back to the source on the compression stroke. If
the check valves are not working right, it will be impossible to build
pressure.
Remember, displacement countered by resistance builds pressure!
No displacement, no pressure. No resistance, no pressure. The fuel lines
always provide some resistance.
No regarding the location of the pump.
If the pump is located higher than the fuel level, the pump is required to
"pump air" in order to bring fuel into the pump chamber. The pump must be
capable of "pulling from draft". i.e. able to lift the fuel up to itself.
Air, being elastic, pumps poorly with this type of pump. The check valves
must be light and tight in order to pump out the air and "prime the pump".
If the pump is below the fuel level, gravity will "wet" the suction side of
the pump, and reduce the performance requirements to only moving liquid
fuel.
If the check valves are perfect, the fuel will be trapped in the pumping
chamber, and the pumping action will start right off.
If the fuel is allowed to drain back each time the pump is off, there will
be some delay in building pressure while the pump builds pressure, and
delivers fuel to the carbs.
Sometimes, with an electric pump you can hear the pump start clicking when
electric power is applied. If the fuel system has no return, you will note
that the pumping action stops after a few seconds. The pressure has built
up as high as it can. If the fuel system has a tank return, the fuel pump
will circulate the fuel from and back to the fuel tank.
My advice? Fill up your tank! Install a transparent fuel filter in the
delivery line just before the carbs so you can see if fuel is making it's
way to where it is required. You did install a good name pump? It should
work at the tank top location.
Did you bypass the mechanical pump, or are you in series?
Regards
Calvin Grandy
Subject: Fuel Pump Pressure
Any thoughts? Oh yeah, I mounted the fuel
> pump above the fuel tank on the back of the trunk. Is this a bad spot?
> Thanks.
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