On Apr 18, 1:18*am, Oren wrote:
On Thu, 17 Apr 2008 20:58:56 -0500, "Don Young"
wrote:







"Manjo" wrote in message
...
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 symptoms sound consistent with fuel starvation. If so, you should be
able to get it to run a bit longer by partially closing the choke or by
squirting a little gasoline into the intake as it starts to die. If that
does not help, you likely have a temperature related ignition failure. That
could be caused by a control module, ignition coil or condenser.

If it is fuel related, first be sure you have good fresh gasoline. Otherwise
there is almost certainly something wrong with the carburetor. Use a
carburetor cleaning spray to be certain that all passages are clean and be
sure you have all the parts correctly installed. If it has one, carefully
check the inlet filter screen at the bottom of the carburetor. A partially
clogged filter could cause it to start after sitting a while but not allow
enough fuel to pass to keep it running.

Don Young

It sounds fuel starved to me. Checking the spark with the plug out and
grounded to the head would tell if there is enough spark (bright blue,
snappy and not a weak yellow). Then I would use a carb /starting
fluid.

As the engine is about to die spray into the carb throat. If the
engine picks up pep, runs higher rpm....check the carb.

*ONE* thing I would be sure to check is the gas line. Look for small
cracks and /or replace.

Next is! How is the fuel filter?- Hide quoted text -

- Show quoted text -

GROUP REPLY (Don, Jeff, jp):

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.

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’m
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. 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’s 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’t 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