Does Lycoming make any sense?

Robert, does it matter whether the boost pump is on or not?


"Robert M. Gary" wrote in message
ps.com...
I just spoke with Lycoming regarding my very high fuel flow. Recently
I've had a problem where I'm getting almost double my normal fuel flow
at idle even with the mixture at the edge of cut-off. I suspected a
servo but called Lycoming. They said I may have a nozzel with a
blockage and the other nozzles are streaming because of it.
Does this make any sense? Could a blockage cause an *INCREASE* in fuel
flow?
I have a JPI fuel transducor wheel that measures fuel flow that has
shown to be very accurate.

-Robert

That is for a different kind of injection system, used by Continental but
not by Lycoming. Lycoming uses RSA which does not have a return-to-tank.

At least it used to be that way.


"jim" wrote in message
ps.com...
If I remember my "mechanical fuel injection 101" there is a "relief
port" of sorts somewhere. The pump delivers enough for the injectors
and then some. The "relief port" orifice bleeds off the excess and
returns it to the tank or the input side of the pump. Different size
ports changes the fuel delivery for different size engines. If it gets
clogged I would think the pump would deliver way too much fuel. Your
system, however, may not be like that. Just a guess.

Jim


On Oct 20, 4:58 pm, "Robert M. Gary" wrote:
I just spoke with Lycoming regarding my very high fuel flow. Recently
I've had a problem where I'm getting almost double my normal fuel flow
at idle even with the mixture at the edge of cut-off. I suspected a
servo but called Lycoming. They said I may have a nozzel with a
blockage and the other nozzles are streaming because of it.
Does this make any sense? Could a blockage cause an *INCREASE* in fuel
flow?
I have a JPI fuel transducor wheel that measures fuel flow that has
shown to be very accurate.

-Robert

Stan Prevost wrote:
Robert, does it matter whether the boost pump is on or not?

No, pressure holds solid at 22lbs.

-Robert

I was wondering if the excessive fuel flow indication changes with pump on
vs off.


"Robert M. Gary" wrote in message
oups.com...

Stan Prevost wrote:
Robert, does it matter whether the boost pump is on or not?

No, pressure holds solid at 22lbs.

-Robert

Your turbine JPI device may only report to the JPI display.
The fuel pressure indicator/fuel flow that was original
equipment shows high pressure is there is a blockage and low
fuel flow. But the higher indicated pressure is also
interpreted as a higher fuel flow.

If you have EGT on each cylinder, checking temperatures and
thus fuel being burned can help determine if the cylinders
are rich or lean.



"Robert M. Gary" wrote in message
ps.com...
|I just spoke with Lycoming regarding my very high fuel
flow. Recently
| I've had a problem where I'm getting almost double my
normal fuel flow
| at idle even with the mixture at the edge of cut-off. I
suspected a
| servo but called Lycoming. They said I may have a nozzel
with a
| blockage and the other nozzles are streaming because of
it.
| Does this make any sense? Could a blockage cause an
*INCREASE* in fuel
| flow?
| I have a JPI fuel transducor wheel that measures fuel flow
that has
| shown to be very accurate.
|
| -Robert
|

"Emily" wrote in message Obviously I can't remember the exact cause, but
I've heard the same
exact thing before...blockage can cause an increase in fuel flow.

It causes an increase in the indication on the OEM indicator which in
actuality is a pressure guage, not a flowmeter. Mr. Gary's system uses a
true flowmeter and a clogged injector line should show a decrease in flow.

D.

I don't think so, at least not very much decrease. I think the fuel will
divide among the functioning injector nozzles. This is why the pressure
increases when one is blocked, the fuel is forced through a fewer number of
orifices, causing a greater pressure drop across them.


"Capt.Doug" wrote in message
...
"Emily" wrote in message Obviously I can't remember the exact cause,
but
I've heard the same
exact thing before...blockage can cause an increase in fuel flow.

It causes an increase in the indication on the OEM indicator which in
actuality is a pressure guage, not a flowmeter. Mr. Gary's system uses a
true flowmeter and a clogged injector line should show a decrease in flow.

D.

"Stan Prevost" wrote in message
I don't think so, at least not very much decrease. I think the fuel will
divide among the functioning injector nozzles. This is why the pressure
increases when one is blocked, the fuel is forced through a fewer number
of
orifices, causing a greater pressure drop across them.

If we are talking about the OEM 'flowmeter', how many transducers does it
have? It would need two to measure a pressure drop. It needs only one to
measure the pressure near the spider. If it has only one transducer near the
spider, and a nozzle clogs, the remaining nozzles won't flow enough to
relieve the increased pressure and the result will be an increased 'flow'
indication.

D.

Stan Prevost wrote:
I don't think so, at least not very much decrease. I think the fuel will
divide among the functioning injector nozzles. This is why the pressure
increases when one is blocked, the fuel is forced through a fewer number of
orifices, causing a greater pressure drop across them.

But there is noticable change in pressure, just in flow. The flow is
very high. I could see that if 1 nozzle was plugged that the other 3
would have increased flow but I can't see that the total amount of fuel
delivered would be double. Fuel flow is measured by a spinning wheel
and is not pressure related.

-Robert

Capt.Doug wrote:
"Stan Prevost" wrote in message
I don't think so, at least not very much decrease. I think the fuel will
divide among the functioning injector nozzles. This is why the pressure
increases when one is blocked, the fuel is forced through a fewer number
of
orifices, causing a greater pressure drop across them.

If we are talking about the OEM 'flowmeter', how many transducers does it
have? It would need two to measure a pressure drop. It needs only one to
measure the pressure near the spider. If it has only one transducer near the
spider, and a nozzle clogs, the remaining nozzles won't flow enough to
relieve the increased pressure and the result will be an increased 'flow'
indication.

The fuel flow measurement does not take into account pressure. Its just
an inline wheel that spins around.

-Robert