915iS Hard 1st Start

dunc

Active Member
Joined
Aug 1, 2016
Messages
285
Location
Crawford, CO
Aircraft
AR-1C 915is, RAF/SH/SC
Total Flight Time
5000
My 915iS with 90 hrs TSN suddenly became hard to start smoothly but only on the first time. It ignites right away, but runs very rough, and requires significant throttle increase to keep running. It smooths out after about ten seconds and runs clean and smooth thereafter. If I do a shut down after smooth running, then the next start is fast and smooth. Startup is very similar to a radial engine where one needs to keep hitting the fuel primer to keep it running until all cylinders are firing smooth. I found a couple spark plugs were darker than all others, and minor lead deposits. I always use 94 UL, with no ethanol. A brass wire brush spark plug cleaning had no effect.

If a couple hours have elapsed, then the first cold start will repeat the initial roughness. Rough running will only achieve about 700 RPM until it runs smoothly.

Suggestions where to look?
 
Your fuel lines are draining back into the tank. There is a return line. Next time run a single fuel pump for longer before pushing the start engine button and see if it starts better. I usually wait till I see 39 psi on the fuel pressure before pushing the start engine button
 
Your fuel lines are draining back into the tank. There is a return line. Next time run a single fuel pump for longer before pushing the start engine button and see if it starts better. I usually wait till I see 39 psi on the fuel pressure before pushing the start engine button
I was using FP 1 which topped out at 39 psi. I just tried FP2 which reached 42 psi for about 5 seconds seconds before starter. Ignited right away, but same severe stumble with 700 rpm max for about four seconds, then ran smooth. Same as previously noted. Fuel pressure remained at 42 psi. Subsequent starts were normal, smooth running at first ignition.

Effectively no change although interesting to note FP2 has slightly more available pressure than FP 1. I have only used FP2 on takeoff and landings.
 
I was using FP 1 which topped out at 39 psi. I just tried FP2 which reached 42 psi for about 5 seconds seconds before starter. Ignited right away, but same severe stumble with 700 rpm max for about four seconds, then ran smooth. Same as previously noted. Fuel pressure remained at 42 psi. Subsequent starts were normal, smooth running at first ignition.

Effectively no change although interesting to note FP2 has slightly more available pressure than FP 1. I have only used FP2 on takeoff and landings.

Yeah the behavior from FP1 and FP2 is all as expected. They are in series so they don't add pressure a lot just a bit. The fuel pressure measured is relative to the airbox pressure. So this isn't pressure related. So this just started doing this and was not like this before? I am trying to remember something like this happening on one of the 915iS gyroplanes and I am trying to remember what it turned out to be. I'll think about it.
Have you charged your battery up on a trickle charger overnight. If not I would do that. It does start on the battery and the second alternator does not come in till it goes to 2500 RPM for 8 seconds. If battery is weak it is not good.
 
Yeah the behavior from FP1 and FP2 is all as expected. They are in series so they don't add pressure a lot just a bit. The fuel pressure measured is relative to the airbox pressure. So this isn't pressure related. So this just started doing this and was not like this before? I am trying to remember something like this happening on one of the 915iS gyroplanes and I am trying to remember what it turned out to be. I'll think about it.
Have you charged your battery up on a trickle charger overnight. If not I would do that. It does start on the battery and the second alternator does not come in till it goes to 2500 RPM for 8 seconds. If battery is weak it is not good.
Battery resting prestart voltage is 12.2 as seen on COM radio. This is historically consistent, and it cranks over quickly. However I can try charging overnight and see what tomorrow yields, but not optimistic.

Yes, this anomaly simply and suddenly started a couple weeks ago. The first time I wondered if I just had not allowed fuel pressure to build - I was using a 36 psi value prior to start. Since it smoothly started right up afterwards I was temporarily happy, until the next time, and the next... This now a consistent behavior.
 
Can you get a read from the FADEC? Is there an equivalent of a check engine light? Sounds like an idle bypass solenoid issue I've had on cars and recently on my EFI boat engine. When it malfunctions the engine will be hard to start. If it starts will run rough until the engine gets out of idle condition by increasing the throttle. It's job is is to let air around the closed throttle-body butterfly valve during idle. It is computer controlled. Replacement fixed on all my issues.
 
I don't know how to read the FADEC. Is some special software and cabling required?
 
I don't know how to read the FADEC. Is some special software and cabling required?
Yes there is a dongle that costs $1200 and they won’t give you software for it till you have taken the course. All the guys who think FADEC is easier to troubleshoot for iS engines should know that.
If there is no Lane A or Lane B light coming on solidly or blinking light then there is no code to read with the dongle. Certification of the engine requires FADEC engines to allow pilot to control throttle setting not controlled by the ECU. That is a FAA requirement as stupid as it may seem. So there is no computer setting the idle RPM automatically.
 
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You are one of about 30 engines with this problem now. Turn on your engine monitor next time you let it rough start and see if #2 cylinder is the cold one according to the egt temps. I have had this problem for 1 and1/2 years since the engine was new and now have 250 hours. I have tried many things sent down from rotax and none have worked and they don't seem to care. Good luck. You can email me to talk privately. hsdjp@ yahoo.com
 
Kitfox - The EGT bars are barely moving and imperceptible if different until the engine fully catches. I can try a laser based temperature probe, but sounds scarey!

I have been using both pumps when priming and this works about 3/4 of time. Hard to tell because you only get one shot at a truly cold start. The second start always fully catches.
 
I have used a cheap thermal temp gun to shoot the exhaust pipes also. I always start and shut off as soon as it fires and it starts fine but very embarrassing to do this at the airport every cold start with a 40+K engine. Rotax is the butt of all jokes at my airport where I'm the only one with one.
 
Rob have you actually contacted any Rotax service station for tech support? Looking for answers for Rotax specific tech questions on RWF is not likely to work. I suggest you call closest service station to troubleshoot and follow their advice.
You seem to not have fuel in the lines and it seems to be draining back and that is why when you prime more, the fuel in the lines builds back up and seems to mostly work but I am guessing here. This also may be related to possible fuel pump issue but again needs to be verified.

Harlan: If you are saying you know of 30 such incidents. Has anyone ever filled out a CSIR for Rotax to officially inform them of this service difficulty pattern? Or has this just been all on web forums with no Rotax technical person officially informed?
I do not see how at a startup EGT will have any relevance. They are cold.
 
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Rob have you actually contacted any Rotax service station for tech support? Looking for answers for Rotax specific tech questions on RWF is not likely to work. I suggest you call closest service station to troubleshoot and follow their advice.
You seem to not have fuel in the lines and it seems to be draining back and that is why when you prime more, the fuel in the lines builds back up and seems to mostly work but I am guessing here. This also may be related to possible fuel pump issue but again needs to be verified.

Harlan: If you are saying you know of 30 such incidents. Has anyone ever filled out a CSIR for Rotax to officially inform them of this service difficulty pattern? Or has this just been all on web forums with no Rotax technical person officially informed?
I do not see how at a startup EGT will have any relevance. They are cold.
Yes sir I did file a CSIR and they sent a man out to download my ecu and I made a video of the rough starts for them that they sent to most repair stations. This is when they found out the number of the problem. Only a couple Kitfoxes out of that number. They came back with you are probably getting vapor lock burn Avgas. In an engine they dont want lead. Haha. I burned 40 gallons straight and it never changed a thing. I have video of my first start ever and It did the rough start. So The engine came from the factory with this problem. So far I have been told to get a bigger battery, check, no help. Start on only B lane, Start only on A lane. Start wide open throttle down to 70%. None have worked. They made a bypass line from #2 injector with the orifice in it to get rid of the bubbles. It was said to work on several engines but it was for testing only and your not supposed to fly with it. It did not work on mine, I had high hopes on moving the bypass line that had helped others. I think its an injector bleeding off but they say no.

The EGT reference was only so the OP could tell which cylinder is missing.
They offer no more help to this point. Warranty??? What is that I ask. Sorry for the rant. I Joined this group in hope that the original poster does find a fix. Harlan

Rough start number one is at the start of this video. The first start was on avgas also.
 
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Call Lockwood.
Yes and talk to Dean Vogel. He will likely have you pull injectors and get them cleaned since your engine sat idle for a while.
 
Yes sir I did file a CSIR and they sent a man out to download my ecu and I made a video of the rough starts. They came back with you are probably getting vapor lock burn Avgas. In an engine they dont want lead. Haha. I burned 40 gallons straight and it never changed a thing. I have video of my first start ever and It did the rough start. So The engine came from the factory with this problem. So far I have been told to get a bigger battery, check, no help. Start on only B lane, Start only on A lane. Start wide open throttle down to 70%. None have worked. They made a bypass line from #2 injector with the orifice in it to get rid of the bubbles. It was said to work on several engines but it was for testing only and your not supposed to fly with it. It did not work on mine, I had high hopes on moving the bypass line that had helped others. I think its an injector bleeding off but they say no.
They offer no more help to this point. Warranty??? What is that I ask. Sorry for the rant. I Joined this group in hope that the original poster does find a fix. Harlan

Rough start number one is at the start of this video. The first start was on avgas also.

Have you ever pulled your injectors and cleaned them?
 
Have you ever pulled your injectors and cleaned them?
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.
 
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