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Subject: 912 starting problem

Author:
Bob P

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Date Posted: Sat, Apr 19 2014, 15:23:08 GMT
In reply to: Barry Edwards 's message, "Starting Problems" on Sat, Apr 19 2014, 10:15:51 GMT

Pleased its sorted :)

Sounds like the choke circuit rather than ignition is to blame. If the problem repeats you might try the following (ideas gleaned from Jabiru engine message boards which use (I think) the same type of Bing carb:

1) Stop the engine at the end of the day by turning off the fuel and letting the carbs run dry. This means that you won't be trying to start the engine next time with really low octane fuel (all the octanes having evaporated away from the fuel left in the (hot) float chamber).

2) Make sure the choke circuit is opening all the way (pull the choke all the way out then check that the choke lever on the carb is fully open)

3) On the jabiru engine the choke circuit (actually a small second carb inside the main carb and tuned to run rich) is only effective if the main throttle is COMPLETELY closed during starting.

4) Fully prime the float bowls before starting the engine by running the electric pump for several seconds. If you can hear the pump "ticking" its "note" changes when the float chamber gets full and the system pressurises. Or if you have a fuel pressure gauge, operate the pump until the pressure increases and stabilizes.

5) Someone speculated that the Jab engine could be "primed" to give a richer starting mix, by first pulling the prop through (say) 12 blades with the electric pump on and the choke fully open (AND THE MAGS OFF)

6) If you still have problems cold starting it may be that the jets for the choke have become partially blocked. I think (could be wrong) that one of the jets is in the float bowl.

Just ideas

Bob

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