Testing; Service; Carburetor Pre-Sets And Adjustments - Tecumseh ECV100 - 120 Technician's Handbook

TESTING

1. After repeated efforts to start the engine using the procedure listed in the operator's manual fail, check for spark by
removing the high tension lead and the spark plug. Install a commercially available spark plug tester and check for
spark. If spark is evident and acceptable, proceed to step 2. If no or weak spark, see Chapter 8 under "Testing".
2. Visually inspect the spark plug for a wet condition indicating the presence of gasoline in the cylinder.
3. If the spark plug is dry, check for restrictions in the fuel system before the carburetor. If the spark plug is wet,
continue with step # 7. Check to see if the fuel cap vent is open. With a proper draining receptacle, remove the fuel
line clamp on the carburetor fuel inlet and pull the fuel line off the fitting to examine the fuel flow and fuel condition.
4. Remove the air cleaner element or air cleaner assembly to visually check that the choke shutter completely closes
or check to see if fuel comes out from the main nozzle during priming.
5. If the fuel flow is adequate and no fuel is evident during priming, the carburetor will need to be removed for service. See
"Service" in this chapter or consult the "Carburetion Troubleshooting" chart if other problems exist. Improper fuel flow
indicates the fuel, fuel line, filter or tank require cleaning or replacement.
6. Check the engine compression using a commercially available compression tester and follow the tester's recommended
procedure. Low compression, a dry spark plug, adequate fuel flow, and a known good functional carburetor indicates
an internal engine problem exists. See Chapter 9 under "Engine Operation Problems."
7. A wet spark plug indicates fuel is being supplied by the carburetor. The engine may be flooded by a restricted air filter,
carbon shorted or defective spark plug, excessive choking or over priming, improperly adjusted or defective carburetor,
or the wrong ignition timing. With the spark plug removed and a shop towel over the spark plug hole, turn the engine
over slowly 3 or 4 times to remove excess gasoline from the engine cylinder.
CAUTION: KEEP ALL COMBUSTIVE SOURCES AWAY. AVOID THE SPRAY FROM THE SPARK PLUG
HOLE WHEN CRANKING THE ENGINE OVER.
8. Replace the air filter if restricted or oil soaked. Replace the spark plug if questionable. Install the spark plug and high
tension lead and retry starting the engine.
9. If the engine floods and fails to start, the carburetor may require service. See the preceding "Carburetion Troubleshooting"
chart for additional causes. If the carburetor is functioning properly the problem may be ignition timing related. See
Chapter 8 under "Ignition Troubleshooting."

SERVICE

CARBURETOR PRE-SETS AND ADJUSTMENT
NOTE: EMISSION GRADE CARBURETORS HAVE FIXED IDLE AND MAIN JETS. THE ABSENCE OF THE ADJUSTING
SCREW INDICATES A FIXED JET OR RESTRICTOR AND NO ADJUSTMENT IS NECESSARY. THE IDLE RESTRICTOR
ON AN EMISSIONS CARBURETOR APPEARS AS AN ADJUSTABLE SCREW. THIS IS NOT ADJUSTABLE AND
MUST REMAIN TIGHT FOR PROPER OPERATION.
The idle on an emission is metered using a threaded
restrictor (see Illustration). Proper torque of this screw is
critical and should be torqued to 5-8 in. lbs. or .5 to 1 nm,
if not, it may vibrate loose. When the restrictor is placed in
the idle circuit passage it is capped with a tamper resistant
plastic cap. Tampering is considered the rejetting or
modification through resizing of the jet. If the jet is
removed for cleaning it must be recapped to prevent
tampering when it is re-installed.
Before adjusting any mixture screws the necessary carburetor presets should be made. Check for the proper governor
adjustments as outlined in Chapter 4. Identify the correct carburetor model and manufacturer to find locations of the high
and low speed adjustment screws. Check the throttle control bracket for proper adjustment allowing a full choke shutter
position. See Chapter 4 under "Speed Controls and Linkage". Check to see if the normal maintenance procedures have
been performed (oil changed, fresh fuel, air filter replaced or clean). Consult microfiche card #30 to find the correct R.P.M.
settings for the engine, or consult Service Bulletin #107 for the revised safety specification for rotary type power lawn
mowers. Start the engine and allow it to warm to operating temperature. The carburetor can now be adjusted.
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