Cub Cadet MTD 70 Series - Manual (Page 44)

61, 65 and 70 Series Vertical Shaft Engines
38
Inspecting the fuel
NOTE: Fuel is the maintenance item most often overlooked by consumers. A lot of fuel systems problems are
caused by gas that is out of date or fuel with too much alcohol in it. When inspecting the fuel:
• Look for water.
• Look for dirt.
• Look for discoloration.
• Sniff carefully to see if it smells like varnish or kerosene.
• Save the fuel to show to customer.
• Look for oil in the fuel.
• Test the fuel for alcohol content.
NOTE: Save a sample of the fuel collected to show the customer.
NOTE: Customers pouring engine oil into the fuel tank seems to be a growing problem.
Test fuel for alcohol
Fuels currently on the market contain a wide array of
additives. Some of these additives oxygenate the fuel.
Oxygenated fuel reduces emissions, and is required in
some parts of the United States. Fuel make-up varies sea-
sonally and geographically. Ethanol is the primary additive
used to oxygenate fuel.
Ethanol in fuel creates a lot of problems for gasoline
engines. The biggest problem is that alcohol attracts and
holds water. This corrodes the metal components of the
fuel system, especially the carburetor. Alcohol also does
not produce as much heat as gasoline when burnt and it
burns at a different stoichiometric ratio. This results in less
power for the engine.
A 10% ethanol (E10) mix is acceptable for MTD
engines. Anything higher than that will result in perfor-
mance issues.
NOTE: E15 and E85 fuels are not to be used in any
MTD engines.
There are several alcohol test kit available commer-
cially. See Figure 4.2.
Generally these kits involve mixing a measured
amount of water and gas together and seeing were the
boundary layer is. See Figure 4.3.
The test kit should come with a chart to compare the
boundary layer height to alcohol percentage.
Figure 4.2
Figure 4.3