Tom,
Keep in mind, no matter how distasteful, the fact that a "...plane safe
to fly..." is not the same as a plane deemed "airworthy".
I suggest you ask the A&P if, in his opinion, the plane is "airworthy"
(given due consideration to its present configuration and approved
documentation) before taking it aloft. Even if he thinks it is, any
FAA person who disagrees can have you "in the soup" for just leaving
the ground in it. The possible insurance ramifications are also
significant.
Best regards,
WRB
--
On Aug 17, 2010, at 21:20, Tom & Susan Crocco wrote:
Hello John,
I'll do the best I can with your questions, but I'm rather new to this
airplane and don't know how it has behaved in the past.
I believe the electric pump is in parallel with the mechanical pump
because you can switch off the electrical pump and there is little or
no change to the fuel pressure. We have been debating whether the
electric pump should be left on during cruise flight, or just used
during take-off and landing. I leave the pump on. Normally, from
what I can observe, the fuel pressure gauge normally reads about 4
psi, give or take, which I understand is about right. There is a
red fuel pressure warning light that is supposed to be off when fuel
pressure is adequate. It is common for this light to "flash" or
blink from time to time with no noticeable change in pressure
indicated on the gauge. I do notice that when the electric fuel pump
is on, there is less flashing and extended periods when the light is
off, so there is a net increase in fuel pressure when both pumps are
operating. I have no idea where the pressure sensor for this light
is, or if it is a separate one from the one for the fuel pressure
gauge. I pretty much ignore the light as long as the gauge is
reading about 4 psi of fuel pressure, although it is disturbing that
the light will flash when the pressure gauge seems to indicate normal
fuel pressure. I don't like things I can't explain.
The carb was recently (May this year) completely rebuilt. This was
before I owned the airplane. I do not know if it has the right float
valve seat, but the A&P who did the work is very knowledgeable about
Ercoupes. At the same time, all the fuel lines were replaced. Over
all, the engine compartment is very clean, neat and organized.
The plane has had an on-going chronic problem with "siphoning" gas out
of one of the gas caps. We have gotten into the habit of not filling
the tank all the way to the top, as leaving an inch or so seems to
stop the siphoning. We have debated purchasing new gas caps. We
recently measured the exact fuel capacity of each of the tanks by
completely draining them, then adding fuel one gallon at a time. Our
wing tanks are exactly 8 gallons each. I noticed that the fuel caps
have the number "9" stamped on each one. I wonder if the caps are
intended for the 9 gallon tanks? Perhaps we have the wrong caps.
I've not been able to find out if there are different caps for
different capacity tanks.
When I had to make my emergency landing after the engine shutdown, I
found that the left tank was empty (Put 7.4 gal in it) and the right
tank still had 6 gallons in it. The right wing fuel cap vent was
found to be completely clogged. I believe now that the clogged vent
caused a vacuum in the right wing tank that could not be overcome by
the fuel pumps, so all the gas was sucked out of the left tank. By
the way, both tanks are interconnected and should drain equally.
When we drained the fuel from the tanks to measure their capacity, the
fuel level remained equal as we drained from one side, but then both
caps were off.
I think that clearing the vent hole in the right cap will allow the
fuel to equalize between the tanks. An A&P is looking at the plane
tomorrow, and if he finds nothing else wrong, I'm going to do some
pattern work to verify that the fuel is being drawn from both tanks.
If it is, I'll consider the plane safe to fly and will add checking
the vent holes to the pre-flight checklist.
Tom
From: John Cooper
Sent: Tuesday, August 17, 2010 5:34 PM
To: [email protected]
Subject: Re: [ercoupe-tech] Re: Fuel System Problems Part 3 fingers
crossed....
As far as your fuel pressure problem goes, is this a new development?
Does it go away if you turn on the boost pump? If neither pump can
produce adequate pressure, since it is unlikely they both are bad, I
suspect you still have a fuel supply problem (or a bad pressure
sensor),
otherwise I suspect one of the pumps is weak.
If you have a Stromberg carb, the pressure feed version requires a
different float valve seat. Make sure you have the right part.
If your boost pump is in series with the engine driven pump, and the
engine driven pump fails due to a leaky diaphragm, use of the boost
pump
can result in a lot of gas being pumped into the engine compartment.
You
are better off plumbing the boost pump in parallel with the mechanical
pump. That way, you need a failure of both the diaphragm and the outlet
check valve before you have fuel leakage.
--
John Cooper
Skyport East
www.skyportservices.net
