4-MIX® Troubleshooting and Repair
Before any repair work is performed on a machine, a thorough evaluation should be made
to determine what parts are actually in need of replacement or maintenance. The service
manuals for
STIHL 4-MIX®
engines outline testing procedures as well as special tools that
are needed to repair the equipment.
The STIHL troubleshooting video and corresponding iCademy module are ideal checklists
to use when performing repairs and will assist the technician in performing a step by step
analysis of the machine.
Repair Procedures: Quick Check
The fastest way to find any major fault is to quickly check for compression, ignition, spark,
and fuel delivery.
;
Use a spark tester to verify that spark is present.
;
If the engine has no spark, the spark plug, the ignition module or stop switch
system is at fault.
;
If the fuel system is completely restricted, the engine may not fire at all when trying
to start it. Squirt some choke spray in the carburetor and try to start the engine.
Does the engine have any
compression?
Is fuel getting to the
combustion chamber?
Does the engine have
spark?
On
4-MIX® engines
, if compression feels low, or if the spark is okay and fuel is getting to
the engine, then do a leak down test.
;
This only takes a few minutes. If the leak down is below 10%, then the combustion
chamber is okay and the running problems are due to something else.
;
If the leak down is greater than 10%, the problem needs to be repaired, as well as
making sure that there are no other faults present.
If leak down is less than 10%
on a 4-MIX
®
engine, check for
faults elsewhere.
If leak down is greater than 10%, the
engine will need service, but check for
any other faults before doing any
repair.
