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Posted by on April 18, 2008, 7:22 pm
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> > > I have a leaf blower that uses a 5 hp B&S "L" head engine. The carb
> > > is pretty simple with a choke butterfly, throttle butterfly, and
> > > rubber diaphragm fuel pump. The carb sits on top of the fule tank.
> > > The carb has no bowl. The governor linakges are clean and the
> > > governor appears to be working fine.
>
> > > The leaf blower was starting to run poorly last fall. This spring it
> > > started right up, but after4-5 seconds after running smoothly at
> > > proper speed, it will slowly loose rpms and finally stop after 15-20
> > > seconds.
>
> > > I have cleaned the pick-up tube, replaced the carburetor diaphragm
> > > fuel pump along with the gaskets between the carb and the fuel tank,
> > > and the gasket between the carb and the engine. I've also
> > > disconnected the engine ground wire that normally kills the engine
> > > when the throttle is tuned full off. But after doing all this the
> > > engine still will not stay running for more than 30 - 40 seconds.
>
> > > Thanks in advance for any tips, suggestions, or coments.
>
> > > Manjo
>
> > The engine starts, revs properly and then dies with the choke
> > partially or fully OFF about the same time. Keeping the choke on full
> > kills the engine faster.
>
> > GROUP REPLY TO Don, Jeff, jp (might be a duplicate post)
>
> > A couple of days ago when I started working on this problem, the fuel
> > intake screen at the bottom of the intake tube in the gas tank had a
> > lot of junk in it. I pulled the intake tube off the brass intake tube
> > and sprayed both with non-residue brake cleaner fluid and blew air
> > through the tubes both ways to clean them out.
>
> > Yesterday, I DID take the gas tank completely off the engine and used
> > filtered gasoline to flush the tank. I swirled the gas in the tank
> > and then poured the gas from the tank into a funnel lined with a paper
> > filter. The funnel/filter were feeding into a clean gas container. I
> > did this several times and I DID get A LOT more debris out of the
> > tank. Most of the pieces were about 1/64th to 1/32nd of an inch.
> > Some stuff was black and other pieces were sand in color. I=92m
> > wondering if stuff is getting TEMPORARILY sucked up against the intake
> > screen killing the engine, then the debris drops back on to the bottom
> > of the tank when the engine dies???
>
> > There is no fuel line and no inline fuel filter other than the wire
> > screeen at the bottom of the intake tube. The carb fits directly on
> > top of and is bolted to the fuel tank and then the carb is bolted to
> > the engine. There's no fuel line. There's a nylon or plastic feed
> > tube from the carb into the tank. There's also a small reservoir at
> > the top of the tank that looks like a idle feed tube with an intake
> > jet at the bottom that I believe feeds the carb's idle circuit. I
> > blew compressed air through all the carb circuits yesterday, but TODAY
> > I will also spray Berryman=92s carb cleaner through all the circuits
> > before putting everything back together.
>
> > I have the air filter off the carb and can see the entire choke
> > butterfly. The butterfly arm sits in a slotted nylon detent that
> > holds the arm in place. As far as I can tell, the butterfly is
> > staying firmly in place. I don't have a tilting problem since the
> > carb has no carb bowl or float.
>
> > I have gotten the engine to run a second or two longer each time I
> > spray engine-starting fuel into the carb intake (at the choke
> > butterfly). But even constantly spraying starter fluid into the carb
> > won=92t keep it running. I have not tried spraying gas into the carb
> > because I'm assuming the starter fluid is more condensed and more
> > volatile than regular gas.
>
> > I hope it is a fuel starvation problem and this will fix the dying
> > problem. If it doesn't, then I'm going to replace the magneto.
>
> > Thanks for all the great tips and replies. Please keep them coming if
> > you see I'm missing anything.
>
> > Manjo- Hide quoted text -
>
> > - Show quoted text -
>
> Got it all back together and it ran just a bit better. The engine
> still runs fine for a few seconds and then start the same decline
> until it stops.
>
> I watched everything and it all seemed to function correctly. I then
> tried pressing down and twisting the spark plug cap and the engine
> "seemed" to run a little longer at proper rpm, but it still died. I
> crimped the spark plug c0onnector and it ran a few seconds more, but
> still died.
>
> My current theory is there's a magneto or spark plug cable problem.
> I'm going to try crimping the spark plug cap tighter and if that
> helps, but doesn=92t solve the problem, I'll take the magneto off the
> engine and check it visually.
>
> Does anyone know how to test a magneto? My magneto is behind the pull
> starter and cover combination, and to gain access to the magneto
> requires removing the cover, but no way to hand starts the engine with
> the recoil starter off the engine. Right now, when I do an ohms test,
> I get 2,500 ohms with one probe on the spark plug cap and the other
> probe against the magneto body. Does anyone know what voltage the
> magneto is creating? Can a standard voltmeter be set-up between the
> spark plug and spark plug cap for a reading, or will the magneto blow
> out the meter?
>
> TIA for everyone's help.
>
> Manjo
When you had the carb apart to change the diaphragm and clean the pick-
up tube...did you shoot carb cleaner thru the jets to see if they are
clear?
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