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TRACING ENGINE TROUBLE
When fuel is available at the carburettor note if (a) flooding has occurred
due to the choke being closed too long, or (b) the choke is nG>t being used
to the fullest extent. If flooding has occurred, the sparking plugs will he
wet with fuel. Allow fuel to evaporate, removing plugs if necessary.
If engine still fails to start, test for air leaks at the carburettor and
inlet manifold by applying oil to the joints while the engine is turned fairly
fast ; the oil will disappear if an air leak is present and it will he necessary
to renew gaskets.
Further refusal to start indicates blocked jets or passages in the
carburettor. (See Page 30.)
When fuel is not available at the carburettor check back through the fuel
system as follows :-Observe whether fuel tank is exhausted and, if fuel
is available, verify that the tap is turned to the petrol position. See that
the vent holes in the filler caps are not obstructed, and that the passage
to the fuel tap is not blocked by seale or deposits from the fuel tank ;
this can be checked by removing the filter bowl, turning the tap to petrol
position. If the flow is satisfactory, check the flow of vaporizing oil in
a similar manner. Examine the filter in the carburettor banjo and while
this is disconnected, open the fuel cock. No flow indicates blocked fuel
ph>es or that the fuel tap strainer may be choked. Remove and inspect.
MEUHANIOAL FAULTS
Engine Controls
These may not be functioning correctly. Examine, particularly for
freedom at joints.
ENGINE RUNS UNSATISF.AOTORILY
Engine fires irregularly-Ignition
This may be due to the sparking plugs being wet, the spark too weak
to fire regularly under compression, or the contact breaker not working
correctly. Check and correct as explained in previous section.
Engine fires i,·regularly
This can be caused by the fuel mixture being either too weak or too
rich.
Partially choked jets, filters or pipes, carburettor not functioning
correctly or an air leakage may be responsi�le for a weak mixture. The
slow running air screw on the carburettor may need adjustment. Investigate
and correct as explained in previous section.
Flooding at the carburettor or a partly closed choke will result in a
rich mixture. Investigate and correct as explained in previous section.
A rich mixture can also be caused by lack of attention to the air cleaner
base, which may he dirty, overfilled or filled with oil heavier than that
specified. Remove the base ; drain, clean and refill with used engine oil.
PAGE 37
