915iS Hard 1st Start

[Abid]

It runs perfect, I do not suspect a dirty injector. I think one is leaking off but Im probably wrong because they tell me it will run on one injector if the other one is bad but it should tell me on the engine monitor. It has never thrown a code to my knowledge.

Remember the start of iS happens on only one set of injectors no matter what so you may run fine but if the start uses one set of injectors it will start roughy and bogged down if those injectors are plugged in any cylinders.

 

[Abid]

Is this a problem only with the 915iS?

I don’t know if it is a problem. If the injectors get gummed up from inactivity it isn’t an engine problem. They need cleaning

 

[Kitfox Pilot]

Is this a problem only with the 915iS?

As far as I know this is only a problem with a very few of the 915is engines. This is the first public statements I have made about it. I was hoping they would come up with a fix but they have not. First it was blamed on a kitfox problem but that was proved wrong after some highlanders and slings showed a problem also. Still it's said it could be a builder problem, I'm not saying I haven't made some kind of mistake but now that my video has turned up the others I am less inclined to think its a builder problem.
According to some reports moving the fuel orifice return line has helped a few that I have heard. That's why I have great hope for that. 200 dollars later to build the line and it didn't help mine I'm very sorry to say.

Not wishing anyone problems but if it was more wide spread they would fix it IMO.

 

[Kitfox Pilot]

Remember the start of iS happens on only one set of injectors no matter what so you may run fine but if the start uses one set of injectors it will start roughy and bogged down if those injectors are plugged in any cylinders.

I did not know this. But I was told to start it on only a lane and only b lane and both still did the same, wouldn't this use different injectors? I didn't think I could work on a new engine under warranty is why I haven't taken and swapped injectors? Also they have told me that's not the problem is another reason I have not.

 

[Abid]

I did not know this. But I was told to start it on only a lane and only b lane and both still did the same, wouldn't this use different injectors? I didn't think I could work on a new engine under warranty is why I haven't taken and swapped injectors? Also they have told me that's not the problem is another reason I have not.

You cannot work on Rotax engines if you are not a trained Rotax tech or the warranty is void. That's true. But where are you getting your technical support for the engine. Who is your Rotax service center and why have you not flown to them and have them look at it? You need to get all injectors cleaned. Most likely my guess is that your engine sat around and the gas you used gummed up just as it does on carb jets.
I am not exactly a "motorhead" but this is just basic common sense stuff. My advice to you would be to contact your Rotax service center tech support (someone like Dean Vogel at Lockwood Aviation) and describe to them your symptoms and work through the steps they provide.

 

[Kitfox Pilot]

I don’t know if it is a problem. If the injectors get gummed up from inactivity it isn’t an engine problem. They need cleaning

My engine has never been inactive if you are posting this towards me. I bought the motor in dec, plane flew in april and has flown 260 hours in the last 18 months since the first flight.

 

[Abid]

My engine has never been inactive if you are posting this towards me. I bought the motor in dec, plane flew in april and has flown 260 hours in the last 18 months since the first flight.

Dec to April sounds like 4 months and your engine was broken in at the factory by running it with whatever gas they use. Gas dries and depending on the formulation can create gummy substance or you may have other debris like the video I posted explains.

 

[martin-av8r]

My engine has never been inactive if you are posting this towards me. I bought the motor in dec, plane flew in april and has flown 260 hours in the last 18 months since the first flight.

Do you find your problem ?

your video is the first start-up of your engine ? after building your aircraft

or it run before , and do you have another cold start video

do you see with other cold start if your engine smoke whitish like in your video

before it clean-up to his normal idle rpm

 

[Henry_GyroLife]

Does that engine have an automatic choke?

Yes.

 

[Kitfox Pilot]

Do you find your problem ?

your video is the first start-up of your engine ? after building your aircraft

or it run before , and do you have another cold start video

do you see with other cold start if your engine smoke whitish like in your video

before it clean-up to his normal idle rpm

The video was the first ever start up. The engine has started the same way now for 1 1/2 years on the first cold start of the day. It does usually smoke a little on that start like unburnt fuel smoke. not as bad as the first start was. I know it's not oil smoke because the engine uses no oil.

 

[Kitfox Pilot]

Yes.

The engine is fuel injected so it has no choke.

 

[Henry_GyroLife]

The engine is fuel injected so it has no choke.

I meant it has automatic chock function. It increases RPM initially after starts up.

 

[martin-av8r]

ok normally when fuel injector pintle leak on shutdown and push the pressure and some fuel from the fuel rail

on the affected cylinder , this fuel puddle in the cylinder , from the back of the intake valves --port injection---

and cause black dark gray smoke on cold startup from over rich fuel mixture

can stumble a bit also from over wet sparkplug also before cleanup to normal idle

but normally if it take enuff time.. days before the next cold start the fuel have time to evaporate

and dont really cause startup over rich fuel problem

if you dont have an inside cylinder head oil drip leak problem , that smoke more white than over rich fuel dark gray black

white ish smoke on start up and some stumble to clean-up to idle rpm can be also coolant pressure leaking problem

accumulating at shut down , normally from head gasket problem but i know rotax dont have cylinder head gasket

and have air cooled cylinder and cylinder head that dont communicate coolant to cylinder

coolant level never drop ?

if it was me to be sure it is not a head casting small pinhole problem , or a very small crack

you can put a pressure cap or sensor on the coolant system to monitor the coolant pressure on the working engine

and how fast it can drop at shutdown and after shutdown , also when cold when the coolant pressure is completely drop

put pressure in the system for some time and wait to see if it is worse at the next cold startup

i know what you explain with the rotax warranty but the first simple thing is to remove all fuel injectors

and have it check and tested on a FUEL INJECTOR test bench for cleanliness , spray patern, and shutdown leakage

can also possibly check fuel injectors pulse wide opening from the efi system with a scope

at cold startup to detect a problem , Rotax dealer or mechanic head need to step-up to find your problem

with very low hours engine

 

[Kitfox Pilot]

I meant it has automatic chock function. It increases RPM initially after starts up.

not that I know of. Only throttle control changes rpm best I can tell.

 

[Kitfox Pilot]

ok normally when fuel injector pintle leak on shutdown and push the pressure and some fuel from the fuel rail

on the affected cylinder , this fuel puddle in the cylinder , from the back of the intake valves --port injection---

and cause black dark gray smoke on cold startup from over rich fuel mixture

can stumble a bit also from over wet sparkplug also before cleanup to normal idle

but normally if it take enuff time.. days before the next cold start the fuel have time to evaporate

and dont really cause startup over rich fuel problem

if you dont have an inside cylinder head oil drip leak problem , that smoke more white than over rich fuel dark gray black

white ish smoke on start up and some stumble to clean-up to idle rpm can be also coolant pressure leaking problem

accumulating at shut down , normally from head gasket problem but i know rotax dont have cylinder head gasket

and have air cooled cylinder and cylinder head that dont communicate coolant to cylinder

coolant level never drop ?

if it was me to be sure it is not a head casting small pinhole problem , or a very small crack

you can put a pressure cap or sensor on the coolant system to monitor the coolant pressure on the working engine

and how fast it can drop at shutdown and after shutdown , also when cold when the coolant pressure is completely drop

put pressure in the system for some time and wait to see if it is worse at the next cold startup

i know what you explain with the rotax warranty but the first simple thing is to remove all fuel injectors

and have it check and tested on a FUEL INJECTOR test bench for cleanliness , spray patern, and shutdown leakage

can also possibly check fuel injectors pulse wide opening from the efi system with a scope

at cold startup to detect a problem , Rotax dealer or mechanic head need to step-up to find your problem

with very low hours engine

Thanks for this info. I was told to put the tailwheel up on a stand at flight level and attempt cold start. 3 mornings it started perfect while in flight level with the tail up. I dropped the tail back down on day 4 and rough start again. I don't know what this means but it's the first thing that has made the engine start right. This is when the fuel bypass line was moved from the fire wall to the #2 injector and back into the return line. This did fix some of the planes that tried it. Not sure why it didn't work for me. Lucky I guess, Haha

 

[martin-av8r]

like i said normally for me rich fuel burn over rich mixture , fuel drawning clean up at startup is more black smoke dark gray than white

oil burning startup more white-blueish smoke than black dark gray , and small coolant drip in combustion chamber problem at shutdown give more white ish steam at start-up

when i see your engine angle from your tail wheel aircraft at rest position , i think can be some small problem also with oiling

system return from the back firewall side cylinder head oil level from emptying return problem

and small leak from cylinder head valve guide or casting problem

i think some rotax cylinder head have some trouble with porous casting in the past

can look weird but try to find with some one to help that know about this with safety at cold start up

to try to find and detect the smoke at start-up smell and look like -- over fuel --- oil burn --- or a bit coolant smell

 

[martin-av8r]

----3 mornings it started perfect while in flight level with the tail up. I dropped the tail back down on day 4 and rough start again. I don't know what this means but it's the first thing that has made the engine start right.----

with this problem detection you find that if the engine rest level at shutdown , to the next cold start-up the problem is eliminated

try with the engine normal back drop , plane on the tail wheel , waiting a good time in this position and before the cold start-up try with a good bore scope to see in the 2 back cylinder if you can see a liquid accumulation or wet stuff in the top combustion chamber and near valves and piston top and around piston edge

 

[Kitfox Pilot]

The cold mis in the engine is #2 cylinder confirmed from my data downloaded by rotax out of my ecu. I have scoped it and have seen nothing. Plugs are all perfect the same. They say it is bubbles , vapor, something resting in that area. They last recommended av gas. Two full tanks of av gas had no change in starts at all. They seem to have given up and I seem to be stuck. I wish there was a lemon law I could send this engine back and get another one. For what I paid for this engine I feel I should not be having this problem to solve on my own.

 

[martin-av8r]

yes you are 100 % correct on this

a bit funny what they say , because normally vapor , bubble , fuel frothing , aeration , boiling

is normally all caused by heat , fuel heating problem , heat soaked engine and fuel system and we know more with mogas than 100LL

but not on a cold start on a cold engine with a new efi engine setup

The cold mis in the engine is #2 cylinder confirmed from my data downloaded by rotax out of my ecu.

if rotax can confirm the cylinder 2 , they dont know more with the super duper ecu... , it is with the injector driver

or the injector , and with the ignition system...

they dont send you new injectors to try ? and new fuel pressure regulators ?

genuine new Bosh fuel injector can be 60 to 75 usd only

is the OP that start this post find his problem... ?

 

[Kitfox Pilot]

I was hoping he had a good mechanic that would fix his problem and I could learn but he has not responded any more about it.
I really didn't want to take over the thread just hoping the OP would run across a solution.
I have had nothing offered from rotax to try other then instructions to make the new bypass line which I did at a cost of just under 200 dollars. And the other advice I stated above. They seem to want to blame it on kitfox, the builder anything except their engine having a problem. Sorry about the vent. Thanks for your help. Hoping the OP finds something.