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1. 06:14 AM - Re: High indicated fuel flow with fuel pump on (N1BZRich@AOL.COM)
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Subject: | Re: High indicated fuel flow with fuel pump on |
Bill and all,
Sorry for taking so long to respond to this question, but with the
turkey day holiday and finalizing the December newsletter (should go to Pete
and Jim today), I have kept busy. Anyway, I also have seen the same
increase in fuel flow when the electric fuel pump is on. I have always just
assumed it was because the fuel flow transducer (like the fuel pressure sensor)
was between the electric fuel pump and the engine driven fuel pump and not
between the engine driven fuel pump and the carb. So I think it is
probably normal to see a rise in fuel flow (as you see the fuel pressure go up
-
if you have the fuel pressure indicator) when you turn the electric fuel
pump on.
Buz
In a message dated 11/25/2009 9:06:51 P.M. Eastern Standard Time,
bill@gdsx.com writes:
--> Lightning-List message posted by: "Bill Strahan" <bill@gdsx.com>
I've been fleshing out my checklist and recently decided to add turning
the fuel pump on for takeoff and landing. I'm used to that with my Grumman,
and it felt natural to do it that way.
Today I took off using the new checklist, and once I was a few miles from
the airport I noticed my fuel flow was 11GPH! I've never seen anything
near that high and my fuel flow already was reading about 10% too high.
I throttled back to a setting that typically shows 4.5-5 gph and was
seeing 7. For a moment, I pictured a fuel leak and decided to turn the boost
pump on and see if the fuel flow surged, which would confirm a leak on the
firewall side, and I was going to immediately return to the airport.
Instead I realized I had left the boost pump on since takeoff and then I
wondered if that was the cause of the high reading. Sure enough, with the
boost pump off the EIS indicated 5.1 gph. Boost pump on and it jumped back
to 7 or so.
I was pretty sure I didn't have a fuel leak at that point, so left the
pump on for a half hour or so while I flew. I saw a growing disparity between
what the totalizer thought I had left and what the tanks were indicating,
confirming to me that the indication is all that was changing, I wasn't
pumping fuel overboard.
So, anyone else noticed the same thing? I would have thought the flow
sensor would have been independent of fuel pressure, but that appears to not
be the case.
Bill
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=274827#274827
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