boolat

hello,

I would check the fuel pressure dle55,
video of my test:

[youtube]http://www.youtube.com/watch?v=SY0g-pMyfNk[/youtube]

normally it should remain on 11psi.
and fall gently until all 5bar.

I do not understand the procedure followed for testing,
could you please help me

try to be simple

thank you

w8ye

My Feedback: (16)

Appears there is a problem with your carburetter

Most of the DLE carburetters have a pop off pressure greater than 15 PSI and they hold the pressure.

Either your needle and seat are leaking in the regulator or the check valve flaps in the pump part of your carburetter are not seating properly.

boolat

DLe55 is a new engine with only 35 flight ...

to better understand the test (pop-off pressure)
could you please explain clearly?

thx w8ye

w8ye

My Feedback: (16)

The pump side of the carburetor pumps fuel with a diaphragm and one way valves actuated by positive and negative pressure pulses from the engine crankcase.

On the other side of the carb, there is a demand regulator that is opened by a vacuum from the engine. If there is no vacuum the regulator will not open the needle and seat valve. This regulator is normally held shut with a spring but vacuum from the engine manifold or from the carb venturi will act on the diaphragm and open the valve.

Your carb has either a leaking valve in the regulator or the check valves (one way valves) in your pump are leaking.

You may be able to correct this problem by putting some fuel in the carburetor to moisten and free up the diaphragms.

w8ye

My Feedback: (16)

How well does the engine run?

boolat

works fine in general,
slowed not very stable
to have a slow I must remain stable in 1850rpm.


during the test I let the hose connecting this:



the problem may come from there?

w8ye

My Feedback: (16)

Disconnect the hose and re run your test?

Tired Old Man

My Feedback: (1)

Was the engine correctly tuned before determining if it ran well or not? First things first.

The pop off pressure is not terribly critical. Anywhere between 12 and 30 psi generally works just fine for our purposes. The pop off pressure is determined by the spring under the metering needle. They are replacable and can be ordered in various strengths. Typically springs are ordered in multiple part kits and experimentation is done to establish the level of pop off pressure required for specific applications.

boolat

I just did the test without the hose....
still nothing happens?
I heard that a normally membrane lever must be open? psiiiitttttt with a little noise!

w8ye

My Feedback: (16)

The pressure is supposed to hold at 12 psi or whatever it is set at unless you press on the outside of the regulator diaphragm and then the pressure is supposed to collapse.

boolat

I am completely disoriented ...
I just want to test without removing the carburetor ..

thank you the trouble that starts very well

jedijody

My Feedback: (1)

The pulse line will make no difference hooked up or not, most critical is the reseat pressure, it should be 10-12 PSI, as TOM mentioned the pop off pressure is largely insignificant if it's over 15 PSI. I would install a K20-WAT repair kit including the inlet needle and re-test, make sure the test is done wet.

boolat

we have in the forum videos of the test pop-off pressure Walbro?

to see before you do anything ....

jedijody

My Feedback: (1)

Not that I know of on RCU, might be able to find one somewhere on line but I don't know why you need one, you have one already and the information you need to fix it. Doing more pop off tests isn't going to fix anything, if you can't take it from here you should seek the help of a local modeler with this kind of experience, or since the engine is relatively new, contact the dealer where you purchased it.

Tired Old Man

My Feedback: (1)

Real simple. Disconnect fuel line, connect pressure gauge line. make sure the bleed valve on the compressor finger pump is closed. Pump up until the gauge reaches a point where the pressure suddenly falls off. Repeat the test, this time going more slowly to see wher that brak point was. Release all pressure, repeat test again to verify the break pressure.

The pulse line means nothing to this test. You cannot perform the test with a "dry" carb. There must be some residual fuel in the carb. If the carb is brand new, get it fuel wet before performing the test. Meaning put some gas in the supply nipple.

In any event, your test video shows a carb that is inconsistent with the pop off pressure but that is largely due to the way the test is being administered. The range of depicted pop off pressures is within what is considered acceptable. You should go fly

boolat

hello,

Now it's normal in your opinion?
I slightly pull on the internal spring.

[youtube]http://www.youtube.com/watch?v=XvNP4RqgkT8[/youtube]

THX

w8ye

My Feedback: (16)

I would venture to say that it was normal.

You are not going through the test properly as you are applying pump pressure too fast and the actual pop off pressure is missed.

The only pressure measurement we are actually seeing is the reseat pressure which is acting more or less normal.

Super08

My Feedback: (2)

If you apply the air pressure slowly it will reach a point where it will stop increasing. This is the pop off pressure. As stated above what you are seeing is the re-seat pressure.

Old Coot

My Feedback: (1)

Was going to say the same as w8ye and others, but check here > http://webspace.webring.com/people/b...daptation.html or here http://wem.walbro.com/distributors/s...viceManual.pdf It will give you a good idea whats going on.
a c&p from that site, faster then me typing it lol.

Pop-off pressure calibration: Pop-off is the pressure at which the Inlet Valve 'pops' open on demand and allows fuel to travel toward the needle jets. It is important to understand the difference between the measured pop-off pressure during a bench test and the actual functional pop-off pressure of a running engine; In a running engine, the pop-off pressure will happen on demand and it depends on various dynamic factors not pressent during a simple bench test. Factors such as fuel demand and atmospheric pressure determine the actual pop-off pressure in a running engine. The one thing we must do regarding setting the pop-off pressure, is setting the correct and critical Metering Lever height. Since we are pressure-testing the carb while subjected to an abnormal (non-running) situation, the measured pop-off pressure will not be the same as in a running engine, but this test can be used for diagnostic purposes:
For example, if the pop-off pressure during the bench test happens at 30 PSI or more, it is too high, and it is indicative of sticky diaphragm flap valves or a sticky Inlet Valve seat.
If you wish to actually pressure-test a Walbro carburetor, prime it as usual and then simply remove the fuel supply line and attach the Walbro pressure tester onto its fuel inlet fitting. [Walbro’s pressure tester part # 57-11 ; $57.42 USD]. Pump air into the system and watch the gage needle drop when the Inlet Needle pops off its seat (opens). You want a pop-off pressure between 14 and 25 PSI
To adjust the pop-off pressure, run a depth gage across the Metering Lever, calibrate the gap to 1.7 mm (WG carbs) and 1.45 mm (WB carbs) below the edge of the carburetor body, no gasket, but does not restrict the gage from moving across it. If you go higher in the Lever, it will give a lot more fuel and it can become a little hard to start because the Inlet Valve will not be able to close in time.

When reassembling, first place the thick Metering gasket on the carb body, followed by the thin Metering Diaphragm. If the replacement parts have the tang & grove metering system, make sure the Metering Lever clips into the Metering Diaphragm.

Inlet Valve Reseat Pressure Calibration: The normal position of the Inlet Valve is closed (the metering spring keeps it closed). The Walbro manual states that calibrating its reseat (closing) pressure is far more important than pop-off pressure! When the Inlet Valve gets unseated (pops open) under fuel demand, it must then reseat (close) at 10- 12 PSI. You’ll know by watching the pressure drop on your pressure gage; After pop-off happens, the pressure drop should end and remain steady at 10 PSI or above. It should never drop below 10 PSI. This will ensure that fuel pump pressure does not override (push open) the Inlet Needle Valve since the fuel pump produces 5-7 PSI.
To increase the Inlet Valve reseat pressure, gently stretch the Metering Spring, this increases the force on the inlet needle seat (shuts tighter). To decrease the reseat pressure, carefully compress the metering spring (careful not to loose it!). NEVER CUT IT!!. If in doubt, replace the Metering Spring (Walbro part # 98-320-7, OEM # 503 28 12-18; WG8 carb).

pe reivers

Ditto the last paragraph.
In the test I see no distinct reseating of the valve. Like W8ye said, this can be due either to a leaking carb needle, OR leaking non-return valves in the test pump (They should seat well, and be installed!)
Anyway, clean the needle tip and seat just to be sure they shut off the fuel flow well.  I never was satisfied with a carb going lower than 12 lbs.

Pop-off is not always a distinct pop, If however pumped up slowly, it can be observed on the gauge quite well.

Antique

My Feedback: (4)

Fuel pressure is a misnomer, there is no fuel pressure in a Walbro..Fuel is drawn from the tank by the action of the crankcase pulses on the diaphram with the flappers..It's a closed system, no pulses can get past the diaphragm...

jedijody

My Feedback: (1)

The fuel pressure is within the carburetor itself while the engine is running,between the pump diaphragm and the inlet needle, not the tank.

boolat

So if I understand.

1: injecting gasoline into the carburetor
2: opens the inner needle injection is stopped
3: Looking on the manometer to the needle stops on 11PSÄ°

right?

boolat

Hello,

Could you give information concerning this:

it measures what? and why? something that has to do with the pop-off pressure?





thx

w8ye

My Feedback: (16)

2. Inner needle is closed and no gasoline enters the venturi

The needle is opened by vacuum in the venturi of the carburetor.

Vacuum is created by by airflow through the venturi of the carburetor