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912iS First Start Issue

BobbyLucas

BobbyLucas

Well Known Member
So we fired up our engine for the first time this weekend, and it did not go well. To start with, I had way too much throttle because I didn't know 50% throttle is only a couple of centimeters of throttle-handle travel. After the fact, I found the G3X screen that showed the actual throttle %.

When the engine finally started, I realized the throttle was too high and pulled it back. There were a few seconds of smooth running, but for the most part, it was shaking pretty violently, so I assumed at least one cylinder was not firing. The Lane A light started blinking and I shut it down and have not tried to restart it since.

I finally figured out how to get the G3x logs this morning and confirmed there's an issue with cyl3 and possibly 4.

The fuse box shows all green lights, at least when the engine isn't running. All cables into and out of the fuse box, EMS, and HIC seem to be fully seated. I guess I can pull them all and make sure each pin is fully seated. Spark plugs are torqued.

Any other ideas, other than the obvious digging into the manuals and calling Van's?
 

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Spoke with Van's... We booted the G3X into config mode and looked at the FADEC entry in System Information, and there were no active faults. They suggested running it again and watching this screen for error messages.

I will keep Lockwood in mind, thanks Mike.
 
Reviewing the graph it looks like you fire it up and the RPM picks up to nearly 3,500 RPM. Looks like you then pull it back to ~1000RPM at 14:29:46 ?

How long did you run it before shutting down is there more data ?

The Rotax engines like to idle high - 1800RPM+ otherwise you will get a horrible rattle from the gear box. It definitely won't like running at 1000 RPM.

It's obviously notable that EGT3 didn't come up but it did come up which suggests something was firing. If you look at everything else fuel pressure, oil pressure is good. I would try again and see if it will smooth out around 2000RPM while you wait for the oil to warm up.

Hopefully I have all the colors right in the charts.
 
That's pretty much it, the graph ends when I shut down both lanes. I hope it's as simple as improper engine speed, but I won't hold my breath. My second hope is that it's just air in the lifters - I haven't checked them yet because you're supposed to run the engine first after the initial oil filling.

The fuel tank is out to fix a leak, but as soon as the sealant cures I will try the engine again, this time at the proper speed. Should I check the lifters first maybe?
 
I seem to remember my engine took two or three 10-15 second runs before it was smooth. I did read but don't know if it's an accurate statement that the Crankshaft position sensors take a few runs to calibrate themselves.

I would bet on all you need is a higher idle speed - it's not your Grandpa's Lycomming ;-) and it takes a little use to running it at an idle of 1800RPM and the reflex is to pull it back to under 1000RPM.

Robert
 
You're starting with just fuel pump 1 running, right?

35% throttle position gives me a perfect startup every time. Idle at 2100-2200.
 
Yup, just pump 1 running. I will shoot for 35-50% throttle and then 1800-2200 idle next time. Fingers crossed.
 
Plugged injectors?

@BobbyLucas, I don't have an RV-12 but I do have a 912iS on an airplane I built but won't name here since some RV builders I have met seem to have an outspoken superiority complex when I mention the model and have been a bit condescending. Perhaps some would say I have an inferiority complex :). Even so, it hasn't tarnished my desire to eventually build an RV.

On my first start, my engine ran almost identical to yours. After much research, I suspected plugged injectors. I called the engine distributor and he said I needed to pay to get it fixed which was likely in the several thousand dollar range since my build took longer than expected and my engine sat for a few years. I decided to DIY it and took apart the fuel rail and removed the injectors. There was some white crystalline powder within the fuel rail and in the injectors. I constructed a mechanism to pressure clean my injectors with carb cleaner for about $5 (or you could spend a lot of money on new injectors at about $1500). I did the same with the fuel rail and regulator. After I put it all back together it ran perfectly. I was also careful to follow the detailed rotax documentation perfectly.

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.
 
Not something I wanted to hear lol. Van's did mention plugged injectors though. What about just using a fuel system cleaner additive like Seafoam? I took delivery of my new engine about 15 months ago.
 
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i dont know about all this , rotax and others talk about a "bad start scenario" it can happen when starting with both pumps on or to high throttle position. It happed to me when i was training in N317VA, ran very rough and lots of clatter from the gearbox. it would not clear with more or less throttle. I shut it down, did a fresh engine start and it ran perfect.

I would just try it again following the checklist. at least try it before digging a big hole! I doubt you could hurt the engine.
 
Ethanol is trash

Fuel cleaner may help your situation, but given the quantity of white powder that I found in my fuel rail in a brand new engine, I wouldn’t risk it. By the way, after much research, I discovered that white crystalline powder is the leftover result of water saturated ethanol based gasoline. My conclusion was that the rotax factory used ethanol based fuel for the initial run and then after sitting for a few years became waterlogged and then dehydrated.

After my experience with this engine, it occurred to me why my ski boat was gradually losing power over the past five years. I decided to remove and clean the fuel rail and injectors, and I had a seemingly brand new engine with twice as much power. I found the same white crystalline powder there too. needless to say, I never again put any ethanol base fuels in any recreational vehicle, airplane, or power tools. I haven’t had any problems with my engines since that time.
 
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Thanks for the input gents. Fingers crossed that Max is right. If not, then hopefully a little fuel treatment can clear it out.
 
Just tried again and now it won't turn over more than once. Voltage was at 13.3. Is that not enough?
 
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Ok, so I found at least one of my issues. The violent shaking from the first startup event over the weekend pulled the engine ground wire right out of its crimp fitting on the battery box.

Lockwood said the high throttle was unlikely to cause the engine behavior I experienced, but my fingers are still crossed.
 
Just a thought from left field here. any chance you mixed up the spark plug wires on the forward and aft cylinders on either side?
 
Ignition Issues

Hello there;

I would check your three wire wiring into the bus, first. It may be that you fired
some part of your ignition? If any Line-A or B is on for only a few seconds, then off, ignition is your problem.
 
rcarsey said:
Just a thought from left field here. any chance you mixed up the spark plug wires on the forward and aft cylinders on either side?
Click to expand...

Nope, all good there.

Van's and Lockwood both said plugged injectors are pretty common. Along with Bkc's experience, that seems most likely at this point.
 
SUCCESS!!!

Installed the new engine ground wire, started up at 40% throttle, and presto!

Thanks for all the help, once again!
 

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