Subject: Intermittent Cold Start Failure – Jabiru 3300A S/N 33A1751
I am requesting your assistance regarding an intermittent cold starting problem with my Jabiru 3300A engine (S/N 33A1751).
The engine has approximately 270 hours since new and remains completely original, including the Bing 94 carburetor and the original ignition system. No modifications have been made.
The problem began approximately 25 flight hours ago and has progressively become more frequent. Initially it occurred only occasionally, but it now happens during approximately 80% of cold starts.
The symptoms are very consistent. During a failed start attempt, the starter cranks the engine normally but the engine shows absolutely no indication of firing. There are no pops, coughs, or attempts to start. It simply continues cranking until the battery eventually becomes discharged.
Once the engine starts successfully for the first time, it operates perfectly. It idles smoothly, develops full power, runs normally throughout the entire RPM range, and performs flawlessly during flight. After that first successful start, it will restart normally, even after remaining shut down for approximately one hour. The problem only occurs during the initial cold start.
The issue is independent of ambient temperature.
The following troubleshooting has already been completed:
Installed a new battery.
Verified proper starter cranking speed.
Performed a complete inspection of the ignition system, including cleaning the magnetic trigger surfaces, distributor caps, ignition leads and related components. Everything was found to be in excellent condition.
Confirmed strong spark on all six spark plug leads during cranking.
Spark plugs are the NGK model specified in the Jabiru manual, are nearly new, and their gaps were verified.
Compression test results are: 77 / 75 / 77 / 76 / 78 / 77 psi.
Performed a complete inspection of the original Bing 94 carburetor. No worn or defective components were found, therefore no parts required replacement.
Fuel is fresh 100LL aviation gasoline with no signs of contamination.
Tested both the mechanical fuel pump and the auxiliary electric fuel pump.
Tried every recommended starting procedure, including the procedure described in the Jabiru manual using the primer only, starting without priming, using throttle pumping, and several other starting techniques. None changed the behavior.
The engine originally came from the northern United States and had an oil sump heater installed. Since we are currently in winter, the heater was reinstalled, and we also preheated the engine thoroughly with a forced-air heater before attempting to start. Neither procedure produced any improvement.
Additional observations:
Spark is always present during failed starting attempts.
Spark plugs show normal fuel wetting after unsuccessful cranking and do not appear to be flooded.
The engine has never exhibited rough running, power loss, misfiring, or any abnormal behavior once it has started.
Every shutdown prior to the appearance of this problem was completely normal.
Based on all the troubleshooting already completed, we have been unable to identify the source of this intermittent cold-start problem.
We would greatly appreciate any recommendations regarding additional diagnostic procedures or any known issues that could produce these symptoms.
Thank you for your assistance.
Best regards,
