Service Manual

Single Stage Snowthrower Service Manual 8 - 1
TROUBLESHOOTING
TROUBLESHOOTING TIPS - FAILURE TO
START
This section is not intended to cover everything that
might happen. We will cover the most common
problems and provide some tips to speed
troubleshooting and repair.
OLD FUEL
By far the most common cause of failure to start is old
or dried fuel due to improper storage procedures. The
correction procedure varies from engine to engine.
The following is an abbreviated carburetor cleaning
process which often will get the engine started.
Tecumseh AH520 And AH600 Series Engines
These engines all used diaphragm type carburetors. In
this style carburetor, there is a nylon check ball behind
the adjustable high speed jet. Storage without running
the engine dry often results in some fuel sitting on top
of this check ball. It evaporates and effectively glues
the check ball down. Fuel cannot pass through the
high speed or power circuit. The symptom is often that
the engine will not run unless the choke is engaged.
Solution
Supplies: A can of pressurized carburetor cleaner with
a small hose which fits into the nozzle. A pump type
siphon and something to drain the old fuel into and
some fresh fuel mix.
Remove the gas cap and using a pump type siphon,
remove as much of the old gas from the fuel tank as
possible. Replace with fresh fuel mix.
Follow the left hand handle down to the engine shroud.
You will find a slot in the shroud and in that slot will be
one or two adjustment needles. On those with two
needles, the one we want is on the right. Those with
single needles it is the only one there. Turn the needle
clockwise until just finger tight (count the revolutions,
this will be important later) then turn the needle
counterclockwise and remove it.
Figure 183 0217-093
Insert the small hose into the nozzle of the carburetor
cleaner and work the hose down into the bottom of the
hole that the needle was in. Hold firmly and spray a
VERY short burst of carburetor cleaner into the hole. If
you held the hose firmly, the carburetor cleaner is
directed into the passage where the check ball is.
Sometimes you can even hear the ball pop loose.
Allow the excess carburetor cleaner to drain, just a
minute or so. Wipe the end of the needle with a rag
dampened with carburetor cleaner and install the
needle. Turn the needle all the way in until you feel it
bottom and back it out the same number of turns that it
was originally.
The engine will be hard to start as the carburetor
cleaner does not burn like gasoline. Go through the
starting process 3 or 4 times. If the engine will start,
allow it to run for at least 10 minutes. The fresh
gasoline flowing through the carburetor will finish the
cleaning.
If the engine will not start after the above process is
followed, the carburetor may need soaking and a more
thorough cleaning. Complete disassembly may be
required.