© STIHL Inc., Virginia Beach, VA     2013 US/STR
confidential
20. Fuel Filter
 It is a good idea to backflow a fuel filter with the pressure 
pump to verify that it is not restricted
 Hook up the tester and place the filter on a towel and pump 
the tester 2 times
 No pressure should build up and if the filter is wet with fuel 
it should clearly flow out
© STIHL Inc., Virginia Beach, VA     2013 US/STR
confidential
21. Pressure Test Fuel Line
 Connect the pressure tester to the fuel line where the filter was 
removed and gently pump it up no higher than 10 PSI
 If it holds steady then the fuel line is OK, and the carb itself
passes the pressure test
 If the gauge does not 
hold then either the fuel 
line or the carb may be 
leaking, so isolate the 
fuel line and test it by 
itself to determine 
where the fault is