Re: Electrical Problem with Main Fuel Pump
by Bill Hertzel » 4 years ago
This is a 914 Engine.
It has 2 identical Electrical pumps plumbed in Series/Parallel.
Neither pump is subordinate to the other.
The Main/Aux designation is Arbitrary.
The Pump designated MAIN Should activate with the MASTER Switch; Not A/B IGNITION Switches.
The Pump designated AUX should activate with a separate Breaker/Switch.
Either pump should be capable of supplying at least 150% of the engines fuel needs.
Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.
Re: Electrical Problem with Main Fuel Pump
by Tyler Hathaway » 4 years ago
Why not have the main pump on its own switch, just like the aux? That way the same one (the "main") doesn't always come on whenever you turn on the Master switch. There may be times, on the ground, when you want Master power on but no pump running. And then, once you are in cruise, you can choose either pump to keep running while turning the other off .
Re: Electrical Problem with Main Fuel Pump
by Wayne Fowler » 4 years ago
Gents where the 914 is concerned you really should have a look at the circuitry as suggested by Rotax.
It incorporates some fancy tricks which allow the main pump to continue to run even when your battery or
main cct breaker are tripped so that if you lose ALL power that pump will continue to run and so will your engine.
Oli I know that you fly a gyro, I just dont know which one and if they supply a wiring diagram (few do).
If you however follow Bills fault finding process chasing voltages you should find the fault. The trick will be if you
have a map (the circuit wiring diagram) as some manufacturers wrap their wiring looms and make it difficult
to follow.
Regards.........Chook. (Western Australia)
Re: Electrical Problem with Main Fuel Pump
by Oli Mueller » 4 years ago
Hi there, I finally found the problem. I followed Bill's advice and checked all items in line. The tricky part was that I mainly checked the impedance with the voltmeter, instead of checking if actually current would come through. The trouble maker was a bad connection at one of the fuses. This means I was checking this fuse 10x or more with the same result: it’s perfectly working and it’s not the problem. Wrong, because what I finally found was that for some stupid reason the cable on one side was not connecting with the fuse. I took it out, made sure that the connection is good and it’s all working perfectly now. Thanks guys, you all were a great help and I do not regret signing up with the Rotax-Forum and becoming a member. Cheers Oli
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