ecrt123

My Feedback: (12)

I have a Brison 3.2 with a Walbro Carb WT 551. I was flying today and after the 3rd flight the engine would not start, I checked the spark plug and it has plenty of spark. But I did notice that the diaphram on top of the carb was not moving at all. I checked the screen and fuel is flowing from the inlet. If I put my finger over the choke plate then the diaphram moves but as soon as I take my finger off no movement. Does anyone have any ideas.

Thanks

Ray

tim220225

My Feedback: (4)

Does it fire at all? If fuel is moving then it is pumping, at least somewhat. Are you sure all the screws are tight annd you have no air leaks? I would look for a cracked spacer block, etc. You say you checked the screen, did you make sure it was reassembled with the diaphragm and gasket in the right order?

Antique

My Feedback: (4)

The diaphragm you can see through the hole is not the pump diaphragm....It moves because when you choke the carb all the suction from the piston going up pulls fuel through the inlet needle...When you open the choke there is not enough suction to do that...The diaphragm on the other side is the pump diaphragm, it is activated by the crankcase pulses, completely separate...The pump fills the cavity under the other diaphragm, then air flowing through the carb pulls fuel through the little holes and high speed nozzle, just like a cheap paint gun...When the cavity empties the diaphragm is pushed down by atmospheric pressure and lifts the lever that lifts the inlet needle to let more fuel into the carb...
Choking the carb lets enough fuel into the engine to run for a few seconds and stop if the pump isn't working because of a pulse leak...

CopperheadAV

Why are you so complicated???

Tired Old Man

My Feedback: (1)

He's teaching. The explanation of how it works goes a long way for some in better understanding of why something may not be working. Knowing how it's supposed to function permits locating where the problem may be by eliminating areas that are not relevant to a particular function.

That, and he may be a little bored tonight

ecrt123

My Feedback: (12)

No I get no fire out of the engine. I have not touched the needles, they are the same. Just funny that it would be running perfect and then after 3 flights it does not even think about starting. When I empty the fuel out of the tank and remove the fuel from the tubing, and then refill the tank it is not drawing fuel to the carb. Do I need a repair kit? Walbro WT 551.

Thanks

Ray

BaldEagel

First check the pipe from the crankcase too the carb and ensure there is some suction there when turning over the engine, it could just be as simple as the tubing has developed a leak, if that checks out Ok check the diaphram for holes, even a pin ***** will stop it working.

Mike

ecrt123

My Feedback: (12)

Yes there is suction. It does draw fuel when I have the choke on and I put my finger over the small hole, but only then. I will inspect the gaskets for holes.

Ray

JoeAirPort

My Feedback: (41)

He just explained exactly how it works, and totally answered the question. What more could you ask?

BaldEagel

Something that has not been asked is where is your tank relative too the carb, I know that some of the walboro carbs on some engines have to have the hole in the choke butterfly soldered up to work properly according to the whereabouts of the tank, try putting a screw in it just to see what happens, I don't need to say don't start it with the screw loose in the butterfly now do I.

Mike

ecrt123

My Feedback: (12)

It never needed that before. All in needed to do was choke flip 4 times off choke and flip 2 times and bam it would run flawless. It looks like to me that there is a fuel flow problem. Do you think that a repair kit would fix this problem?

tim220225

My Feedback: (4)

The tank can be about anywhere as there is a pump. Not like a glow engine. Still think you have a leak somewhere or bad diaphragms somewhere. Does the engine have an external pulse line? A piece of tubing running off of a tap in the case or carb spacer block running to the carb plate? If so check that piece of tubing for a crack.

ecrt123

My Feedback: (12)

No external pulse line.

TLH101

My Feedback: (90)

Are you sure it's not getting any fuel. If it runs fine and won't restart, sounds like it may have lost spark. Possibly a bad trigger, faulty switch or wiring to battry, ot even a low or dead battery.
Just a thought.

ecrt123

My Feedback: (12)

Has very good spark with 2 different plugs so no fouling. When I put the choke on no fuel to the carb, but when I put my finger over the hole in the choke plate here comes the fuel dripping out the the carb.

Ray

tim220225

My Feedback: (4)

Take the cover off and inspect the gasket and diaphragm. Note the order you take things off. Should be cover then the diaphragm and then the gasket. Have you looked at the space block to check for cracks?

ecrt123

My Feedback: (12)

I will do that tonight and see.

Ray

ecrt123

My Feedback: (12)

The bottom of the Carb is wet and the bottom has fuel in it. The intake on the engine body has suction. I inspected all the gaskets and I could not see any holes, the screen was clean, and I checked the space block no cracks or leaking. But still no fuel being drawn into the carb with the choke only, it draws fuel only when I put my finger over the hole in the choke plate.

Ray

nonstoprc

My Feedback: (90)

If the small hole is covered and the fuel is flowing, will the engine start?

tim220225

My Feedback: (4)

Try this directly from the Walbro serivice manual. Squirt fuel into the spark plug hole and try to start the engine. If the engine fires then you have good spark and compression for the engine. Next try squirting fuel into the carb throat if it fires the problem is most likely in the carb or fuel system. Here is a link to the manual. Page 9 and 10 of the manual is where you need to look. Keep us posted. This is a PDF file so you can save it to your drive for the future.

Walbro Service Manual (PDF 5.8MB) http://www.wind-drifter.com/technica...viceManual.pdf

This link has some interesting ideas regarding midrange RPM

http://www.geocities.com/farellus/idle_adaptation.html

ecrt123

My Feedback: (12)

Thanks for the links very informative. I will try that method tonight when I get home.

Ray

ecrt123

My Feedback: (12)

Well I did what you said tim and it fired up with 1 flip. So I will be sending in for repair, thank goodness that it is still under waranity.

Ray

Tired Old Man

My Feedback: (1)

Did anyone ever suggest checking the connection of the fuel line at the clunk, inside the tank? A leak here is always a problem. Then there's the pick up line where it attaches at the outside of the tank. Sucking air at this location is another biggie. No zip ties or other securement devices at the tank pick up tube almost assures that it's sucking air after the gas line has aged bit.

tim220225

My Feedback: (4)

Glad you have fire. Try what Silversurfer suggests before you take the engine out. Probably a very simple fix. Again look for any possible crack or break in the intake and fuel system and make sure all 4 bolts for the carb and intake are tight. The two for the intake manifold block are under the carb so you need to remove the carb to get to them.

ecrt123

My Feedback: (12)

I checked the tank and lines, even changed them out with fresh tubing and changed out the stopper. No leaks there so I bought a carb kit for my carb changed out all gaskets and parts. I checked out the suction from the engine again strong there. I looked at the gaskets on the engine to the carb no cracks or leaking their either. So after much fustration I sent it in for repair. It is still under warranty and I just thougt I could fix it instead of sending it in. Thank you all for such great ideas and you taught me some very good tricks and information.

Ray