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Paul,
I have two MSD pumps as well. At least one
should run continuously to keep your fuel line at the proper pressure for
injection. They will actually produce close to 80 psi with no flow.
So a pressure regulator is needed. I run both on take-off and landing -
should one fail there might not be time to react if only one was
on.
In the automobile (I just replace the in-tank fuel
pump in my van several months ago), the pump does turn on momentarily when you
turn on the key. This is simply to pressurize the line AND to provide the
initial fuel for starting. If the engine does not start the pump stays
off, if the engine starts, the pump turns back on - but, you can't hear it over
the engine.
My HALTECH unit had a similar set up. It
simply opened or close a pump relay depending on whether it sense engine
rpm. If the engine rpm was zero the relay would not close thereby
preventing you from pumping fuel into the engine and out the tail pipe if the
engine was not running. I presume your MicroTech system has something
similar.
IF it does, I would wire one pump to the relay -
use it for starting - and the other pump would have a power toggle switch
that I controlled - my personal opinion of course.
Ed A
----- Original Message -----
Sent: Monday, May 02, 2005 10:47 AM
Subject: [FlyRotary] fuel pumps
Hi all....I need to ask a question regarding the
two EFI fuel pumps. (I have two MSD pumps, I think they are something like 65
psi each). Should these pumps run continuously? I know that on my
automobile, when you first turn the key (ignition), you can hear the fuel pump
run for a few seconds to pressurize the system, then it sounds like it shuts
off. On our aircraft, should they also do this or should they run
continuously, since the unused fuel is returned to the sump tank after the
fuel pressure regulator? I know that my MicroTech system has the wire
that supplies power to the fuel pumps going to a relay first, then the power
leaves the fuel pump relay and goes to the fuel pumps.
I know that most of you
have Tracy's ECU system, but if I recall correctly, I think that Ed Anderson
had used an automotive ECU (another brand) prior to changing to Tracy's
ECU. Just wondering how that system worked, regarding the fuel
pumps.....constantly running or on demand.
Thanks in advance for
any and all info you guys might have regarding how the EFI pumps are supposed
to work. Paul Conner
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