912iS Starting

Two lanes on

One pump on

Lanes are not pumps

Have both lanes (ECU's) on and one pump.

My planes SOP is

Master and Avionics (G3X) on,

Both lanes on, wait 5 seconds for the ECU's to boot.

Aux pump for 5 seconds to build fuel pressure, switch off, and hit starter. That way the fuel pressure is up to almost the correct number when you hit the Starter.

I have an EarthX battery and the volts do not drop below about 13 Volts during the start, so plenty of Amps to spare.

Always starts within a couple of seconds

Hello there,

I may be a bit late for this topic. I just finished to build my RV12 iS and I had the same issue during the first engine run-up and few more other times. The first start attempt was always bad, ending up with a weird engine running (like it was running  only with 1 or 2 cylinders) or not starting at all.

I did few tests (tried also with both fuel pumps on) but so far the only solution that seems to work out is to turn one fuel pump on, let it run for few seconds to allow any fuel vapour in the fuel line to be purged out, set the throttle to 60% - 65% and turn the key. With this the engine starts pretty good and then runs really smooth. I just did few starts sequences so I need more to see if the sequence "solve the problem". The engine is brand new and I have no previous experience with the 912iS.

The Rotax OM says to switch both lanes on and only one fuel pump on. Wait for 3 Bar fuel pressure  and set the throttle around 55% - 65%. There is also an interesting graph (page 3-9) showing the best throttle positions (the one you read on the EFIS not the actual throttle lever position) according to the engine oil/coolant temperature... at -25 degrees celsius minimum 55% throttle position is needed to have a good start behaviour. Theoretically according to that graph you can set the throttle to 100% and  this would be good to any condition for a good engine start. (obviously not ideal with a cold engine running at high RPM).

Will see how it goes with the next start attempts.

Cheers

Whenever I hear of someone who has a rough engine on the first start, I plead with them to clean their injectors as well as the entire fuel rail. I have heard of numerous instances of bad fuel left in the fuel rail by the factory and plugging the injectors. It also happened to me and cleaning the injectors and fuel rail made a world of difference. 

In fact, if I ever purchase a new iS type engine again, I will flush the fuel rail and injectors before my first start.

Bryan Casper wrote:

Whenever I hear of someone who has a rough engine on the first start, I plead with them to clean their injectors as well as the entire fuel rail. I have heard of numerous instances of bad fuel left in the fuel rail by the factory and plugging the injectors. It also happened to me and cleaning the injectors and fuel rail made a world of difference. 

In fact, if I ever purchase a new iS type engine again, I will flush the fuel rail and injectors before my first start.

I was planning to do the same - flushing. Are there any difficulties during disassembling the rail and injectors? Should I disconnect the battery before this process? 

I didn't have any difficulties but I followed the manuals perfectly. It was a bit challenging flushing out all the white powder from the fuel rail.