Testing The Afterfire Solenoid - MTD P90 series Shop Manual

P90 Series Vertical Shaft Engines

Testing the afterfire solenoid

An afterfire solenoid that is not working properly can prevent the engine from starting. The solenoid itself rarely
fails, usually there is some type of fault in the wiring to the solenoid to prevent it from energizing.
To determine if the afterfire solenoid is faulty:
1. Test the unit's battery.
• The battery must be fully charged before any
testing can be preformed.
2. Turn the ignition key on and off while holding the
afterfire solenoid.
• An audible click should be heard and a "thump"
should be felt when the key is turned on.
• If the thump is felt or the click is heard, the wir-
ing is most likely working properly. Bench test
the solenoid.
• If nothing is felt or heard, investigate the wiring
before condemning the solenoid.
3. Check the ground lead of the afterfire solenoid.
NOTE: Running a jumper wire from the negative
post of the unit's battery directly to the sole-
noids ground lead is the fastest way to test
the ground. See Figure 4.20.
NOTE: Do not try to ground the solenoid housing.
The coil inside the solenoid is insulated from
the housing.
4. Repeat step 1.
• If the solenoid is now working, repair the
ground connection.
44
Afterfire solenoid
Figure 4.19
Jumper wire
Figure 4.20