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Help us solve a weird Rotax problem!

Ironflight

VAF Moderator / Line Boy
Mentor
OK, this might be the first time I have ever posted in the R-12 forum…. But I just don’t have much experince in working on Rotaxes (except in my old jet ski days), and I have a neighbor with a problem in his -12 that has the whole airpark stumped.

For several months, on numerous flights, he has had his oil pressure indication drop to zero after some time in flight. He has changed out the probe with a new one, and has the same symptoms - good oil pressure until sometime in flight, then it drops off to nothing. He’s pretty well convinced that he still has oil pressure, because the engine has eaten itself yet! We haven’t put a mechanical gauge on it, because we haven’t started throwing metric parts and fittings into the tool box.

Now here is where it gets weird. About the same time, his right EGT has started to go high after “some time” in flight. He swapped probes (left to right) and the problem stays with the side (right). he told me that “the spring on the exhaust looks liek it has gotten very hot at some time” - which makes me think he really does have an EGT going high on that side. Carb problem that manifests after the engine has ben running awhile? Induction leak that manifests itself after the engine has been running awhile?

He’s ready to start chasing the problems up into the “magic box” or the Garmin EIS….but I think he’s got a real EGT issue and I have no idea about the oil pressure.

I’m stumped - let’s hear from you experienced Rotax types!

Paul
 
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It is likely a wire connection / ground problem. Because of multiple symptoms it is likely some kind of intermittent ground issue.
 
My friend had the same oil pressure issue with his Tecnam. Turned out to be a pin/connector issue at the EMS module
 
Check the wire crimps, and even go as far as cutting and re crimping, could be loose or not enough insulation was stripped off the wire causing intermittant contact...been there before with my oil pressure.
 
Oil Px rate-of-change?

It's sort of implied in the description, but when the oil px goes to "zero", it goes all at once? Or does it slowly work it's way down?

I concur with the other comments . . . likely a wire/ground/termination problem.
 
Check the spade connector at the oil pressure gauge, underneath the gearbox. Clean it up with CRC electrical contact cleaner and then some 000 steel wool. Adjust tension of crimp with some needle nose pliers, so it fits on oil pressure connector quite snug. After installed, put some high temp atv silicone on it to hold it in place.

Make sure the oil pressure gauge is not leaking oil before doing the above.
 
Paul, when your friend sorts out the ground issue, you really need to post here more often. RV12 guys are really a friendly bunch ;)
 
Paul--is the oil pressure sender remotely mounted? Certainly sound like a grounding issue, but I defer to the electrial guys.
Tom
 
Turn on as many electrical loads as practical.
Connect one lead of a voltmeter to a free ground pin on the electronic engine monitor.
Connect the other lead of a voltmeter to the negative terminal of the battery.
The voltage between these two points should measure very close to 0 mV (within 5 mV).
If it does not, you must improve the ground connection between the ground of your battery and that of your avionics.
Also make sure that the engine and battery are well grounded to the airframe.
Paint on the aluminum under the grounding screw can cause a poor connection.
 
OK, this might be the first time I have ever posted in the R-12 forum…. But I just don’t have much experince in working on Rotaxes (except in my old jet ski days), and I have a neighbor with a problem in his -12 that has the whole airpark stumped.

For several months, on numerous flights, he has had his oil pressure indication drop to zero after some time in flight. He has changed out the probe with a new one, and has the same symptoms - good oil pressure until sometime in flight, then it drops off to nothing. He’s pretty well convinced that he still has oil pressure, because the engine has eaten itself yet! We haven’t put a mechanical gauge on it, because we haven’t started throwing metric parts and fittings into the tool box.

Now here is where it gets weird. About the same time, his right EGT has started to go high after “some time” in flight. He swapped probes (left to right) and the problem stays with the side (right). he told me that “the spring on the exhaust looks liek it has gotten very hot at some time” - which makes me think he really does have an EGT going high on that side. Carb problem that manifests after the engine has ben running awhile? Induction leak that manifests itself after the engine has been running awhile?

He’s ready to start chasing the problems up into the “magic box” or the Garmin EIS….but I think he’s got a real EGT issue and I have no idea about the oil pressure.

I’m stumped - let’s hear from you experienced Rotax types!

Paul

1. Re-carbs running rough....

Have the carbs been balanced recently? How many hours on carbs? 200 hr/5 yr overhaul at lockwood + Marvel blue epoxy floats has solved most of my problems in that area. Make sure balancing tube is on properly. I actually think 90% of the problems of the RV-12 can be solved with a proper balancing using a pneumatic gauge type balancer - I usually aim for 3500 RPM - that keeps it tight. Van's RVator had an old article on initial RV 12 run about a rough running engine that the choke circuit was involved with....see if i can find it.

RE - EGT

I have had a EGT probe go wonky and fail. Carry a spare now. Could be electrical but I would look for leaks. Was he in the affected range on the recent exhaust SB? Also has he switched out to the high quality Rotax stainless steel exhaust springs? Available at Spruce and others - swear those dropped my temps. Weird huh.

Oil Pressure -

Assuming he has oil...lol. Then definitely electrical. Could be a stuck bouncing ball bearing in the pressure sensor - follow the bouncing ball...lol.

Has he attached a ground from engine to grounding point by battery? Most of us have and that seemed to work well to stamp out many of the electrical issues...

Good luck.

Update - found a few things...trips down memory lanes....one was the misplaced O-ring on the rubber carb receptacle....other 2-10 page 9 covered using the choke to trouble troubleshoot a blocked jet. Again if the carbs have any age on them send them in for overhaul. Mine were at 5 years with less than 100 hrs and engine ran like new when I got them back! Lockwood did a terrific job.
 

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^^^^^ Perhaps a re-read of the OP... The guy's problem is intermittent oil pressure reading on the EMS. I doubt carb balance of exhaust springs would be my first place to look...
 
^^^^^ Perhaps a re-read of the OP... The guy's problem is intermittent oil pressure reading on the EMS. I doubt carb balance of exhaust springs would be my first place to look...

I like to cover all bases! ;) Saves energy. ;)

Yes I saw two issues. EGT and oil pressure.

I’m guessing a proper grounding might help.
 
Hi,

That happened to me a year ago and the problem was the wire from the oil presure sensor to the instrument, the fault was intermittent works fine on ground and failed in flight.

Check for cracked or crushed wire, do not rule out mouse activity.
 
We had similar issues with an older RV12 (2011) and it turned out that the Vans fusebox/connection board had errors and I had to bypass the sensor wires and make direct connection to the EMS to fix the problem.

I understand that this does not directly has anything to do with the EGT indication, I diagnose these with a standalone thermometer to verify the sender/EMS indication.
Of course it is possible that the EMS has an internal failure.

Good luck hunting down these gremlins!
 
Just to close the loop on this - my neighbor read through the thread, and together we looked for potential grounding problems. Cleaned up a few places where ground wires were on painted surfaces, and also where the Van’s control box was mounted on the (painted) shelf. He did some ground runs, and all was OK, so today he took it flying, and all measurements behaved!

I told him that given the nature of electrical problems, he should fly it a couple. More hours before he celebrates to heavily - but he’s definitely headed in the direction of goodness….

Paul
 
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