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Help, please. I'm in the process of buying a ELSA with a Rotax 100HP 912ULS. The current owner ALWAYS plugs in his Tanin engine heater for 3-4 hours prior to starting the engine regardless of the outside temperature. The sales rep and I thought he was "babying" the engine and didn't think much of it. The owner moved back east and when we went to take a test ride in the plane we did NOT pre-heat the engine prior to trying to start it.

We could not get the engine to start regardless of what we tried. The outside temperature was about 90F. Choke on throttle closed, choke off throttle closed, choke on throttle cracked, etc. Aux pump on, aux pump off, both mags on, one mag on, the other mag on. We could smell fuel so we thought we had flooded it. We finally started to wear the battery down and stopped.

We pushed it back into the hangar, plugged in the heater and charged the battery. One hour later it started after cranking for about 5 seconds. The resulting test flight was uneventful and engine ran fine. The following day I returned with a CFI who owns a 914 and has flown numerous 912's. Once again we tried starting with the temperature about 90F. The CFI used his standard warm weather starting procedure, choke off, little or no throttle. No start, not even a pop. He then tried various combinations and just like the previous day we were unsuccessful. We finally gave up.

The current owner swears we ALWAYS need to use the pre-heat. I say there's something wrong if the engine refuses to start without pre-heat. I could see pre-heat being needed below 40F, but not at 90F. Engine started fine after our short test ride.

My next step is to find a Rotax specialist in my area to give it a pre-buy inspection. The problem is everyone I called is too busy for at least the next 2 weeks. In the mean time, can anyone give me an idea as to what's going on? The current owner stands by the pre-heat procedure because according to him it's needed to help vaporize the fuel. My thinking was no, in warm weather it should not be needed and his overall start procedure was wrong.

Any input will be appreciated. I'll start searching for a tech first thing tomorrow but I'd like some feedback on what others think is going on.

Regards, John
  • Re: Hard start unless heater used

    by » 7 years ago


    It should fire up pretty quick without preheating at 90 F.
    Possibly not getting fuel? Carbs dry? Low or high wing? Low wing may require the auxiliary fuel pump on to fill carbs. Battery condition? Need a good battery.

    Good luck.

  • Re: Hard start unless heater used

    by » 7 years ago


    There is a problem with certain ignition modules that require application of a heat gun prior to the first start of the day. Remove a spark plug, or use a spare, install the wire, making sure to maintain contact with the intake or head and the spark plug, and have someone turn the engine over with the starter. Of course, do this for the first start of the day, without the use of the engine heater, and use all caution to avoid the propeller. Allowing the engine to turn without grounding all ignition wires will cause damage to the ignition box. If there is no spark your modules should be replaced.

  • Re: Hard start unless heater used

    by » 7 years ago


    Hi John,
    Take it to a Rotax mechanic that knows what they are doing. This is either a carb setup issue, poor starting technique or a primer system vs a normal choke setup or maybe all three.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Hard start unless heater used

    by » 7 years ago


    Thanks Roger. This is so frustrating. There is no external primer, the enrichener cable is running to the carbs, and the smell of gas is evident while trying to start. Whether they are properly synched or not I don't know at this point. I know the owner adjusted his carbs at some point and he could have them screwed up. I wasn't was under the impression that un-synched carbs would cause rough running but didn't think would cause literally impossible starting without the pre-heat. I'll start looking for a Rotax tech.

  • Re: Hard start unless heater used

    by » 7 years ago


    Alan, I will check that out. My first thought was that there was no spark or no gas. With the smell of gas after cranking, I felt gas wasn't the problem unless it was being flooded. His starting procedure has alway been give it a little throttle, which defeats the purpose of the enrichener. So when the CFI with Rotax experience couldn't get it going, we were stumped. The engine doesn't fire at all, not even a minor bump. If it is an intermittent with the ignition, it could be the external heat is enabling it to fire. This definitely needs the attention of a Rotax expert. Thanks for your input.

    John

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