Rotax 912 switched to Fuel Injection. Engine still wont run Right. Any ideas? 

So how did we get to this stage ? I was waiting to see the results from one of your previous comments about you having taken the valve covers off. Did this guy you sent your engine to actually have findings? Please reply, thanks.

Im interessted as well did you have any updates?

*Good Idea. An over heated engine could take much of the temper out of the springs especially the exhaust-valve-springs.*

That and valves might not be seating properly or hard enough or too hard.

I concur.

@@garyt6591 *I had this happen and it drove me CRAZY! It turns out the Exhaust valve springs where so weak they where sucking in hot fumes from the exhaust manifold and giving me a crapy burn at high RPM!*

@@johnsluggerunbelievable- I sold a plane because I couldn't figure out this issue. And dumbass mechanics couldn't correlate why an rpm drop with overheating.

that's my first thought too... is there a crank position sensor?

@@banzaiib He said the same problem existed before the installation of the fuel injection system. Wondering what is controlling the spark on the engine. Is it magnetos or something else? Anyway, that is where I would focus. I do automotive performance and never really saw spark plug issues until the last couple of years and now see it all the time. First things I do now when I have an ignition issue is to change the plugs. Most of the time that fixes it. If it doesn't then time to start digging further. I fly planes, but really don't know about magneto ignition system. Can't pass the mag check then someone else figures it out.

*It depends on the local Geology of the rock in your area but SOME OF THE DUST out there can be super electrically conductive! I'd start by cleaning the outside of the wires with a rag that has some Shaving-Cream applied on it to disrupt any static charges and clean them.*

Rev limiter going off...?

Checked it.

5000rpm...broken valve springs? This has been going on for a LONG time and the top end is not damaged?

Maybe not broken, but weakened? Heat tempering from overheat can cause it.

i was thinking a valve spring / sealing issue oddly enough i just fixed a Honda pressure new low low hours with odd running issue ported head lapped vales re jetted drill out one size up it in and now its golden but lol, God bless frUm east tennessee

So where are we at with this issue ? Did you get to run it yet ? Has the weather been good enough to fly it yet ?

Checked, all good.

Thank you!!

Tom was a good watch on your channel! But, he left us hanging how many fat girls had been in that back seat 😂😂

This was my first thought

@@jeremymason1684I'm assuming they've checked the basics like huge plug gaps or broken valve springs.

Agree issues is fuel delivery, hoses, vacuum or pressure. Something in that is probably the issue. Maybe even fuel tank problem. Pressure and vacuum test all the fuel systems: hoses, rails, injector connection points, pump pressure, tank pick up, flared fittings or dissimilar metal connections (example: brass to steel, hose barbs). Fuel injection fuel delivery is pretty complicated and MUST be perfectly efficient through all rpms with flow input and return correctly designed and calibrated. Since this was a carbed engine before may have had different fuel line requirements. From hearing it run in the video at 5000+ it does not sound like a “miss” but a starve for fuel, fuel restriction issues.

Is it at almost 6,000', like this one? I've seen it, looks like fun, I know Troy, my kind of pilot!

Thanks for the update Tom!

I am leaning towards the valve spring issue, after chasing down rabbit holes for the last 2 months (could be this, could be that, anything is possible) BUT I do have a non stock cam, developed by Hal Stockman and installed by him about 900 hours ago.

generally speaking a vacum gauge should bounce at higher rpm or any rpm depending on how bad it is. but by the time it hits 5k and to stumble vacume will bounce so its a test you can do but experience is key @@portnuefflyer

The same prop the last 2500 hours, it's not the issue.

have you figured out the problem yet @@portnuefflyer

The EDGE comapany site does a pretty good job of that.

It's called a Ruffian SEND-E, made in NH.

Rotax 912 series engines do not have timing chains

Might be...

What was wrong with the camshaft, was it worn out?

@@Ayastracci It may have been defective, but the lobs, one in particular, were badly worn, clearly visible when eyeballing it.

If it was fuel starvation the AFR would start climbing to a very lean condition indicating lack of fuel causing a reduction in RPM. It’s gotta be ignition related.

Would agree about the AFR going lean in a carburated setup as you dry out the bowl at high flow rates, but FI with fluctuating pressures at high pulse rates could hold back max power with starvation without showing up in the AFR which is an average over time.

Also possible fuel flow issues maybe a breather valve out of the fuel tank is partially clogged....

Can't hurt I guess, but the gap on new plugs is already at a minimum, as it was when the issue started. And that gets back to "why doesn't switching the mags effect any difference when it craps out" issue, which would seem, unless BOTH sides of the electrical system were at fault, which is really unlikely.

It’s out of gas. Yep….

The crapping out issue has been ongoing for a couple months before I installed the EFI.

Did that, months ago.

@@portnuefflyer Do it again with separate eyes.

As did I, for over 3000 hours, plus a BigBore low comp from Hal S., totally trouble free and then this issue came out of nowhere. BUT, progress of a sort just now: I enlarged the supply line from my 3 gallon header to the fuel pump assembly, from 1/4" (original) to 3/8", and got rid of a un-needed valve that added even more restriction. Pumps like to push, not suck, and though my in flight fuel burn will be the same or less as before (I had a HacMan Leaner), the FI will be moving a lot more fuel, I missed that fact and the runup I just did since increasing the supply line went great. But a static runup for a couple minutes is one thing, still need to fly it, WX permitting.

@portnuefflyer Progress is great! I’m curious though, what about the changes you made would have made the running condition a sudden change with the original components? The fuel lines and valves would have continued to flow the same amount of fuel all the time unless something suddenly got caught in the system causing a slight blockage or a valve had gotten moved slightly slowing down the fuel flow. Additionally, was the fuel line hard line or were there sections of rubber line? I have seen rubber line close up on the suction side and limit fuel flow.

​@@tw6896 Partial hard line, a short section of new 1/4" hose, all good, and flow testing at the firewall pre EFI install showed the usual flow rate, many times more than needed for normal operation. Inspection of the header tank finger screen, the first time I had pulled it in over 3000 hours, showed zero accumulation of any foreign objects or debris.

@portnuefflyer Ok. The reason for my question is I’m trying to help figure out why you had a successful run up after you changed the fuel supply lines from 1/4” up to 3/8”. I’m assuming that is the first successful run up since the issue began. So, if I read your issue correctly, you said that initially the engine ran just fine on the original 1/4” fuel supply lines. Then at some point, it began experiencing the running issues above 5,000 rpm and that has remained constant until the 3/8” supply swap. If it continues to run fine on the new fuel lines, something had changed in the old system because initially it ran good on that system too. It seems to me that only a blockage or restriction of some sort could cause that issue to pop up all of a sudden as long as you didn’t alter the fuel tank venting in the process. That blockage or restriction could have been a foreign object which you said you could not find. It could have been something wrong with the valve you removed. It could have been a slight collapsing of the fuel hose under heavy suction. I have had multiple instances of fuel hoses collapsing under suction over the years. It is nearly impossible to detect as well because as soon as the heavy suction is removed, it springs back out. I have also had fuel hose separate internally such that only the inner lining of the fuel hose was collapsing and the outer section of hose never changed. Regardless I’m hoping it’s still running better after the fuel supply change as you initially indicated. If so, something in the old supply system had “gone bad.” If it continues to run poorly, then you can disregard all of this.

nope

No, but I built it and can work on it, legally, with what they call a repairmans certificate.