Tecumseh Carburetors, In Midway, Alabama
This article aims to educate the reader on two very important aspects of a car. These two components need to be maintained at optimum conditions to avoid car trouble, especially at odd times.
Two of the very important components of a car engine are carburetors and batteries. We shall discuss the working concept of both devices and how to troubleshoot the common problems that may occur due to them.
In order to understand the functions of a carburetor you first need to understand the logic behind starting up your car. It requires a mixture of fuel and air in an optimum amount so that the spark created by the spark plug starts the engine up. The carburetor is responsible for creating this mixture. Therefore, if the fuel composition is too high in the mixture then the engine will run "rich" causing it to not start at all or waste fuel. And if the air composition is too high then this will cause engine damage in addition to not starting the car as well.
In order to minimize emissions and fuel wastage most new cars nowadays come with fuel injection systems instead of carburetors.
Think of the carburetor as a tube with a throttle plate placed parallel along its length. This throttle plate allows air to flow at a high velocity so that enough vacuum is created into the juncture from where fuel can be sucked in for the engine to start up. When the engine is switched off, the throttle plate covers the air vent to prevent the air from entering.
By: Kimyia Varzi
This troubleshooting book is designed as a quick reference for carburetion problems and an aid in identifying failures
and their possible causes. It also directs the user to other publications and printed material that assist in properly
resolving problems or making adjustments not related to carburetion but could affect carburetion.
Listed below are some basic DO'S and DON'TS to be followed when making carburetor repairs.
Follow all instructions carefully.
Use new service replacement screws (650506 Torx 8) for the choke and throttle shutters (screws are treated
with a dry-type adhesive to secure them in place).
Use Tecumseh Power float tool 670377 or an 11/64 drill bit to set the proper float height. Remove the bowl
gasket and measure from the casting surface. The gasket should be replaced or poor starting may result.
Use only genuine Tecumseh Power service parts.
Remove all welch plugs, o-rings and non-metallic main nozzles before cleaning carburetor in cleaner.
Use drill bits to clean passages.
Soak carburetor in a cleaner over 30 minutes.
Reuse original choke and throttle shutter screws.
Interchange bowl nuts.
Reuse gaskets and "O" rings.
When troubleshooting a carburetor, other areas such as valves, fuel tank venting or gaskets should not be
overlooked. The carburetor is dependent on the proper operation of the engine to do its job. The first step in
troubleshooting is to determine if you have a carburetor or an engine problem.
In order for the engine to operate properly, the following items need to be checked first:
1. Make sure there is a sufficient amount of clean, fresh fuel in the tank.
2. Check spark plug for proper reach, gap and condition. Replace, if needed, or in question. Perform an
ignition test using spark tester part number 670366 to assure that you have a crisp spark.
On older point ignitions models check for proper ignition timing according to the Technician's handbook.
3. Check for fuel flow restrictions into the carburetor. Deteriorated fuel line, and fuel cap venting are some of
the more common restrictions. Tecumseh Power uses a stainless steel 75 micron filter screen molded
into most tanks. It is extremely rare for this area to become restricted and should be checked last.
4. Check compression by first disconnecting the spark plug lead and ground it to prevent start-up. Next, turn
the engine over by hand. A definite resistance should be noticed on the compression stroke. Using a
cylinder leak down tester is also possible.
After these basic checks have been performed and you are satisfied with the engine's condition, attempt to start it. If it
does not start, remove the spark plug and check its condition. If it is dry, you can assume there is a problem with the
carburetor or the fuel system. Continue by troubleshooting the carburetor.
IF THE ENGINE IS TO BE UNUSED FOR 30 DAYS OR MORE
Tecumseh Power strongly recommends the use of fresh clean unleaded regular gasoline in all engines. Unleaded
gasoline burns cleaner, extends engine life and promotes better starting by reducing build-up of combustion chamber
deposits. Reformulated fuels containing no more than 10% Ethanol, 15% MTBE, 15% ETBE or premium gasoline can
be used if unleaded regular gasoline is not available. Leaded fuel may be used in countries where unleaded fuel is not
available. NEVER USE FUEL CONTAINING METHANOL.
Gasoline (Fuel) vapors are highly flammable and can explode. Fuel vapors can spread and be
ignited by a spark or flame many feet away from the engine. To prevent injury or death from fuel
fires, follow these instructions:
• Never store the engine with fuel in the fuel tank inside a building with potential sources of ignition such as hot water
and space heaters, clothes dryer, electric motors, etc.
Gasoline can become unstable in less than 30 days and form deposits that can impede proper fuel flow and engine
operation. To prevent deposits from forming, all gasoline must be removed from the fuel tank and the carburetor. An
acceptable alternative to removing all gasoline is adding a fuel stabilizer such as Tecumseh Power Ultra-Fresh part
number 730245 to the gasoline. Fuel stabilizer should be added to the fuel tank or storage container. Always follow the
mix ratio found on the stabilizer container. Run the engine at least 10 minutes after adding the stabilizer to allow it to reach the carburetor.
Draining the Fuel System
IF THE ENGINE IS TO BE UNUSED FOR 30 DAYS OR MORE
Do not attempt to pour fuel from engine or siphon fuel by mouth. Empty fuel tank by using a
commercially available suction device designed for use with gasoline. Then run the engine until
any remaining fuel is consumed. Doing so may result in death or serious injury.
Drain the fuel into an approved container outdoors, and away from any open flame or combustion
source. Be sure the engine is cool.
If gasohol has been used, put a small amount of unleaded gasoline into fuel tank and repeat preceding instructions,
then run engine until fuel is used up.
Oil Cylinder Bore
1. Remove the spark plug wire from the spark plug. NOTE: Always ground the plug wire when disconnected.
Pull the starter handle slowly until resistance is felt from compression pressure, then stop. Slowly release
starter tension to prevent the engine from reversing due to compression pressure.
2. Remove the spark plug, squirt 1/2 ounce (15 ml.) of clean engine oil into the spark plug hole.
3. Cover the spark plug hole with a shop towel and crank the engine over slowly, several times.
4. Replace the spark plug and tighten. Pull the starter handle as performed in step #1. The piston position
blocks the cylinder ports on 2 cycle engines or closes the valves on 4 cycle engines, preventing air from
entering and oil from leaving the cylinder bore during storage.
5. Re-connect the spark plug wire on the spark plug.