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PH3300i SM, Rev. 2017-01-20
5.1.3 Backfire Prevention Solenoid (BFP)
The backfire prevention solenoid is located on the bottom of the carburetor bowl. Its purpose is to
shut off the fuel when the engine is turned off to prevent post-shutdown backfire and run-on
(dieseling). If the backfire prevention solenoid is suspected of being faulty, measure the
resistance between the leads as detailed below.
1. Measure the resistance of backfire prevention solenoid between the two leads of the
green connector (Fig. 37). This connector can be accessed by removing the control
panel (Fig. 38).
2. To bench test the BFP solenoid drain the carburetor float bowl, unscrew the BFP and
remove it from the carburetor. The needle on the end of the solenoid should be in the
retracted position (Fig. 39). Apply +12V to one of the solenoid leads, and ground to the
other (polarity does not matter). The solenoid should make a click noise, and the needle
should move to the extended position (Fig. 39).
3. Replace the BFP if the resistance does not fall within the specified range, or it fails the
bench test. Make sure the end of the needle is clean before installing.
Resistance value
7-
9Ω
Fig. 37
Measure resistance
between these pins.
Access BFP connector
behind control panel.
Fig. 38
Fig. 39
Extended
Retracted
