Cub Cadet MTD P90 Series - Manual (Page 48)

P90 Series Vertical Shaft Engines
42
Afterfire solenoid
When an engine is turned off, the engine does not “instantly” stop spinning. As the engine slows down, it is still
drawing fuel out of the carburetor. This raw fuel passes through the engine because the ignition system is grounded
to prevent the spark plug from firing. When the raw fuel reaches the hot muffler it can ignite, resulting in an afterfire.
An Afterfire solenoid is an electromechanical device that prevents fuel from reaching the main jet in the carbure-
tor when the ignition key is turned to the “off” position. Generally this will prevent an afterfire. Fuel will still be drawn
into the engine from the idle port, but the fuel/air mixture will be too lean to burn.
NOTE: If the throttle is moved to the idle position when turning off the engine, the fuel/air mixture ratio will be
in a range that will support combustion resulting in an afterfire.
To remove/replace an afterfire solenoid:
1. Remove the carburetor by following the procedures
described in Chapter 3: Air Intake System.
2. Disconnect the ground lead using a 10 mm wrench.
See Figure 4.16.
3. Disconnect the power lead.
NOTE: The oil dipstick can be removed for more
access to the power lead; however, it can be
difficult to re-install the dipstick tube without
shearing the O-rings.
Figure 4.16
Ground lead
Power lead