Fuel System OverPressure 912IS

[rosslr]

Paul, what type of throttle cable do you have? From what you describe it sounds like it could be the throttle - I have a mc Farlane type and if the friction on the vernier is not tight it will creep forward and increase revs but not dramatically - it sounds like your kink in the cable could be a problem and need replacing. HOWEVER, that does not necessarily explain the Lane A light coming on. I am not expert but FWIW I would:

1. eliminate any possibility of a faultly throttle cable by ordering and installing a new one.

2. check all the spark plug leads are attached properly

3. Then suspect injectors - my understanding is that Lane A controls half the injectors and spark plugs and Lane B the other half.

Beyond that, I am clueless.

good luck

r

[Jaguar56]

C57C0A6D-0A25-4CC3-9DEB-B1358CD62372.jpg

My throttle linkage. Hopefully the picture worked. It was not linked, just seemed to bend a little prior to going full throttle.

[Jaguar56]

Update. Last weekend I pulled the fuel system apart and checked the filter again. As I had done before I blew in the filter and there seemed to be no restrictions. I lubricated the throttle cable a bit and went up again. Using the pump 2 the pressure never got above 44.5. No alarms. Maybe it is happy again.

I was curious and cut open the old filter. Here is what is inside.

[Jaguar56]

I really thought I had it. Flew for around 3hrs with multiple stop/starts and no issues. Pressures on pump 2 stayed in the 44 range. Last short flight and just leveling in cruise at 1500 AGL the engine started to rev up, fuel pressure went up, Lane A light and “land the plane” warning came on.

It almost felt like the throttle snapped open quickly, it freaks the system out, then settles down. But the warning lights will stay on until I restart the engine.

Not sure what is going on.

[dcsfoto]

I have not done a first engine run yet But , I have a Stock Flight Systems EMU and the first thing in the manual is to hook up a analog fuel pressure gauge and set the offset up

I have a rotax fuel pressure sender and it is indicating 15 psi and I have not put fuel in yet

David Kelm
7SS 912iS

[Av8r_Sed]

Your Rotax sender sounds suspiciously like it's sensing atmospheric pressure rather than "gauge". Not a problem if the electronics adjusts for it.

[Jaguar56]

Your Rotax sender sounds suspiciously like it's sensing atmospheric pressure rather than "gauge". Not a problem if the electronics adjusts for it.

I am really starting to feel it is nothing so complicated. I flew for almost 2 hours on Friday with no issues. But I was very closely watching any throttle movements. I worked the throttle full stop multiple times prior to engine start and all throttle movements during flight were much slower than normal.

Considering how quickly the events would happen and then settle down I really think it is the throttle cable bunching up slightly and then snapping to full throttle quickly as the bunch straightens out. I did see this happen once with the cowl off while working the throttle. This would explain the sudden rpm change and the increase in fuel pressure as the engine suddenly asked for a lot more fuel. And it would explain the warnings to the system and things settling down quickly after the event. And it would explain why the rpms would go up without a throttle movement in the cockpit.

I will keep working it with this in mind and post here with findings.