Intermittent cold-start problem on original Jabiru 3300A Gen2 – looking for anyone who has experienced the same symptoms.

[Mikelius22]

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,

[mkennard]

What battery did you buy? I found the Oddessy hopeless in winter. Since buying the Moto brand, I get the RPM to start everytime.

[facthunter]

Some Plug gaps as supplied, may be too wide. Try reducing them to say .022"  Nev

[skippydiesel]

7 hours ago, Mikelius22 said:

Subject: Intermittent Cold Start Failure – Jabiru 3300A S/N 33A1751

 

• Installed a new battery. Check for sufficient cold cranking amps - more is better

• Verified proper starter cranking speed. How did you do this?

• 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 at HT connection to plug does not indicate plug sparking normally.

• Spark plugs are the NGK model specified in the Jabiru manual, are nearly new, and their gaps were verified. Check for plug spark

• 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. If rubber components old (even if never used) replace

• Fuel is fresh 100LL aviation gasoline with no signs of contamination.

• Tested both the mechanical fuel pump and the auxiliary electric fuel pump. If float chamber has fuel, pump not required for starting

• 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 Bing 94 does not have a choke in the conventional sense  - its uses an enrichment circuit. Check for choke lever action - must go to Full On stop. Throttle nil or just started (if panel knob  - max 12 mm out )

• 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. Preheating only required in extreme cold 

Additional observations:

• Spark is always present during failed starting attempts. How do you know this?

• Spark plugs show normal fuel wetting after unsuccessful cranking and do not appear to be flooded. Wet plugs are usually an indication of overrich mixture (should not be wet)

• 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.

• Check air filter for contamination. Try an engine start without filter.

It seem likly you are flooding the engine and or carburettor rubber parts need replacing. Good Luck!

 

😈

 

 

[facthunter]

The choke doesn't work if the throttle is open too far. Cold engine means cranking speed is lower particularly at the time the spark is supposed to fire. That's why I suggested setting the Plug Gap closer. Having the throttle open more  loads the starter as more gas fills the cylinders and has to be compressed.  Nev

[tillmanr]

Isn't the correct cold start up- No throttle, full choke?

[facthunter]

That's where I would start from on a cold day. Nev

[skippydiesel]

35 minutes ago, tillmanr said:

Isn't the correct cold start up- No throttle, full choke?

Mostly - however many find that a smidgeon of throttle works better than none.

 

I have very little jab experince  - don't think they don't have the "soft start" auto ignition advance, of the Rotax, so a little throttle often helps to get the cold engine straight into fast idle. Its also important to keep cranking the engine, until start has been established - To many pilots let the start button/switch go, on the first cough of the engine.😈

Edited 10 hours ago by skippydiesel

[facthunter]

Your advice there can impose a lot of Load on the starter mechanism. I would NOT advise it.Nev

[BrendAn]

how did you verify the cranking speed. are you sure the reading was correct.

you have to get to 300 rpm for the ignition to fire although if it starts ok warm that probably rules the starter out.